Yellowing leaves, to worry or not to worry?

So I’ve had this blueberry in recipe 420 soil since about Mother’s Day, I live in Northern California and I’ve watered with my PH give it take 6.3. Definitely within the 6.0-6.5 range. I used ff grow big during veg and just recently started using ff bloom bc I seen it started flowering. I’ve noticed yellowing on these leaves. The leaves seem to get light green then yellow then they get brown and then if I haven’t picked them off they just fall off. I thought it was a nitrogen deficiency so I watered with ff grow big, cal mag, and ph to 6.3. They seem to still be showing up, but not as fast. What could be my problem? I have never flushed my plants, but I think if that were the case it would have a build up of nutrients or maybe not. I NEED HELP!!

A few leaves yellowing during flower is normal, you’ve got a few more than I’d consider acceptable.

If you’re using fox farms nutes you should follow their flush schedule. At the minimum at least before flowering?

Do you have runoff numbers… pH and ppm? Your actual soil pH may be lower than pH 6.3

Nitrogen absorption falls off the closer you get to pH 6.0, and certainly below that.

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I just watered last night so I’ll have to check next watering, but I’ll have to buy that sledgehammer since I am about a week or so into flower or so I think this is my first grow. I’ll get back to you with those numbers and hit it with a sledgehammer flush. Thanks for the reply.

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I’ll offer up an opinion. I think you have vegged so long there is no nutrients left in the soil. When you reach that point you need to get a lot more aggressive with feeding.

Fox Farms Big bloom, despite the name, isn’t the bloom formula. It’s a mild, general nutrient that is given throughout the grow. Tiger Bloom is actually the flowering formula. Grow Big has lots of nitrogen compared to Big Bloom and Tiger Bloom and is for growing. Yellow leaves are a sign of nitrogen deficiency. A certain amount of yellowing and dying off is to be expected during flowering, but yours is excessive.

You need to follow the Fox Farms feeding schedule. At this point in your grow you should be using all three of the above. I would be aggressive with the feeding and make sure I was using it every other watering and even exceeding the recommended dose until you get caught up. Alternatively could add the Fox Farms powders which provide considerably higher concentrations of nutrients.

Just one opinion, others will hopefully give you another perspective.


Sledgehammer is not 100% necessary. It makes it easier, but it’s not essential You can use properly pH’d water (6.5). Run 3x-5x the container size of water slowly through it. When the runoff hits 300ppm± you’re done. Be sure to subtract the water’s ppm from the total, (ie. Input water is 88ppm, stop at 388ppm runoff).

Then finish with a balanced mild feed, and feed according to schedule after that.

Runoff numbers during each feed/water will help you keep an eye on how enriched the soil is.

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I agree with @CMichGrower. To add to their comment, that looks like patterned nitrogen toxicity. It starts from the center out, which is the nute path most plants use to grow bigger. Check your nutes, give it a drink of plain ph’d and neutral water at the next watering and see what ya get. You can’t go wrong with a dose of unadulterated water from time to time.

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I’m no expert but my plants can show slight nutrient burn feeding between 1/4 and 1/2 strength FF trio according to the schedules posted above, so I would suggest trying 1/4 strength a couple of watering in a row and see where you are… if you watered twice in a week at 1/4 strength it would effectively be 1/2 strength as the FF schedule above tells you the maximum you should feed in a week.

Summary: FF trio is strong.

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plants will not all respond the same to feeding. If the plant shows a nitrogen deficiency the first thing we do is determine the soils ph as that dictates the soils absorbtion of available nutrients. If the reading of the run off is not cool, it should be corrected becore any nutes are given. No point in feeding a plant whose soil is out of whack. In many cases, what we see as a deficiency is in fact a lock out, the food may be there? Maybe too much? Its just not accessible to the plant. Thats why ph is so important to always keep within an acceptable range.


Okay, so pretty much my first step is to check my soils ph and make sure it’s within 6.0-6.5 and I would do that just by feeding with pure ph water and getting the run off ph?


Yes, run off at least a few cups of water and test that to see what the range the ph of the soil is, and then while you are at it what EC is coming out too. Im assuming you have pens for each test?.

In theory it shouldnt matter if you ph your water in, so long as you know its ph. I would always ph my water to the target ph and then see what comes out, then we decide if a flush in order before we attempt to feed. Does that make sense?
What you should do though is fill out a support ticket, so others here can play along. There are many fantastic growers here that can help you.
I made a small mistake in what I wrote before… ph in your soil is what determines the availability of nutrients a plant can uptake. If you look at a ph chart, you will see that if your ph is 7 some nutrients on either end are barely available if at all. However, the hart does not tell the user that the elements on either end are used in very little quantities by your plant. That said, if you need access to a specific mineral, you can swing ph a tad one way or the other. Typically 1 full point in ph is a pretty big swing.
If your target is 5.8 and your actual ph is 4.8 that is a pretty big swing towards acid! Conversely if you target is 5.8 and your actual is 6.8 thats a big swing towards basic. You can see that 1 point swing either way can add up to either 4.8 or 6.8 now thats a big swing !

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You can also do a slurry test.
Take 2 tbsp soil from a few inches down, preferably near the roots. Don’t chop through the roots though.
Add to 3oz distilled or RO water.
Mix well.
Mix well again.
Wait 15-20 min.
Then measure pH. It’ll give a pretty accurate reading on your soil pH.

If you take ppm/tds readings on your runoff, it’ll give a good indication of how nutrient rich the soil is.

Sometimes one nutrient ends up too high and will lock other nutrients out. Calcium-magnesium-potassium. They will mess with each other if you give them too much of one.
This is why I recommended a flush. It’s basically a reset.

Okay everyone that has commented and chimed in to help out. The results are in. I just fed with approx 6.37 PH and I let the first run off run or what not and then I used a top to a tote container. Then I poured it into the bucket I usually use to mix water and water my plants before putting that water in a watering pot. I came out with approx 6.64 PH and approx 306 ppm and 624 ec I think. I usually don’t measure that bc I’m not exactly sure what is a good reading, but here are my numbers. If someone Can proved me with a support ticket I can fill it out. Thank you. Maybe these numbers can help.

water going in
readings coming out

So your soil pH is probably a little high. Keep giving it pH 6.2 until you start seeing runoff around pH 6.4. Then just adjust the input to pH 6.5 after that.

Your ppms are really low. Time to up the feeding. You’d like your runoff at at least 700ppm right now.

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