Calcium Deficiency?

I have a nutrient deficiency with one of my plants. Details:
Strain AK-47
Soil: Fox Farm Ocean Forrest
PH: 6.5 – 6.7
Light: Apollo Horticulture LED Grow light 400w X 2
Pot size 4.5 gal
RH% 45-55%
Temp: 78-82 degrees
Indoor only
A week ago I re-potted this plant because it was getting big and I started to notice some browning on the leaves (see picture). I ‘THINK’ this is a calcium deficiency, but I cannot be sure as the symptoms are easily confused with other problems. I have 3 other plants which were germinated and planted at the same time in the same type of soil (FF) and none show the characteristics seen in this one plant.
All 4 plants are growing fast – my concern with taking any kind of action is; I am not 100% sure what action to take and I do not want to flood it with nutrients or other stuff before I ask some people who have greater experience with a diagnosis.
For a calcium deficiency I have Dyna-Grow Foliage Pro. My plan to address this problem is to flush the soil with approximately 10 gal of water, measure the run off PH then add a tablespoon of Dyna-Grow to 1 gal of water and water it. I’ll use that for several days and see where I stand after a week or more. I realize the leaves with brown spots will not turn green and I’ll have to watch newer growth for repeat symptoms. I can also easily get some garden lime or dolomite lime - just not sure which one to use.
Any further suggestions?

Are you sure it isn’t a toxicity? You could have a build up of salts in your soil. Some soil probes available at local garden supply/nursery can check more than just moisture or pH and can give you an idea of the EC (electrical conductivity) or nutrient concentration in your soil This can also be done with a digital pen meter and the run off would be measured in a similar way to measure runoff for pH with a digita pH pen.

How old is plant?

Is this fresh soil?

I’ll answer your questions as best I can:
Are you sure it isn’t a toxicity? I have no idea and no idea of how to answer that question accurately.
You could have a build up of salts in your soil. - Doubtful - but still have no way to make this assessment. The Soil is fresh Fox Farm Ocean Forrest and has not had any nutrients added as of yet.
To address your question if I have a conductive meter - yes I do - This is the one I am using - simple but effective
How old is plant? One month
I checked run off with a digital pen meter and received PH reading of 6.2 using this:
ATC Pen meter

I do have 3 other plants which are fine - this is the only one with problems.
What I plan to do is this
I have some Dolomite Lime
Dolomite Lime here
and plan to use a new 4.5 gallon pot, add some fresh Fox Farm soil and mix in 1/2 cup of dolomite lime, add water, let it sit for a day or so, then replant the sick plant, and wait for a few weeks and see what happens.
If you have other suggestions or would like to see additional pictures I can provide them.

That soil probe only checks pH and moisture. You need one that also checks nutrient concentration or “soil fertility” like this:

Or a digital pen like this to test the run off:

Using these, you would easily be able to make the assessment of a toxicity or over fertilization or build up of too much nutrient salts (fertilizer), but as you said you have not added nutrients, then this is likely not the case.

I would not add Lime, that will make your pH go up and you want it around 6.5, maybe even slightly below, 6.7 normally should not cause any problems as you are generally safe as long as you don’t go much above 7.0.

Knowing that you have not added any nutrients and the pH is good, I am thinking it is more a potassium or phosphorous deficiency. Starting a regular feeding schedule with a balanced NPK ratio should help.

Any suggestions on a nutrient or will Dyna-Grow Foliage pro be sufficient at 1 tbl spoon per gallon

I’m not familiar with what is in Dyna-Grow foliage pro, does it have potassium and phosphorous in it? What are the NPK ratios at the recommended dilution? If I had to research and learn every single different nutrient system out there I’d never have time to do anything else. I’m old school, I can grow with miracle grow plant food for tomatoes and a few additives and get top shelf results, nitrogen is nitrogen and potassium and phosphorous are potassium and phosphorous, you take care of these nutrients and make sure some of your micro nutrients are taken care of as well as your macro nutrients and pH is good and and nothing is too strong and you should be good to grow.

As I stated above. With Foxfarm soil; It is best to use Foxfarm nutrients. Usinf Fowfarm soil; It is generally recommended to start a nutrient regimen after one month. so This might be your issue.

I like the idea you have of replanting the plant in a bigger pot with more fresh soil. I don’t think you need to soak it and let it sit with D.Lime overnight, but, hey…whatever.

You also may waht to keep in mind that all plants are going to be different from seed. Only clones can be judged side by side.

@Latewood & MacGyver:
Yes - I completely agree with your suggestion to use FF nutrients, and to start a nutrient regimen at or close to a month of growth. The main thing I learned from this experience with a different strain I have not grown before is:
Don’t over react
Don’t do anything stupid
Different strains ‘may’ have slightly different nutrient requirements (probably the most important)

The problem I originally described was a Calcium deficiency. Under the LED lights it looked a lot worse than it really was. I started a nutrient regiment starting at .5ml / gal then went to 1ml / gal, replanted in a 10gallon soft side container with FoxFarm. I am using Dyna-Grow and not the FoxFarm product - I’ve used Dyna-Grow for a couple of years, always found it to be a good product - plus I have 1/2 a gallon left so I’ll use it up and then look at using the FoxFarm product. The plant has virtually exploded with new growth and shows no new symptoms. I have removed the lower water leaves that were affected by the calcium deficiency.

Anyway - thanks a lot for the suggestions on a ppm meter - that helped a bit - something I never had any need to use.