Is this light burn?

Northern lights regular.

Started Indoors under 65 watt HLG LED. I put them outside a few days with no regard for hardening off and ever since this one has looked like this:

One of her/his sister/brothers:

Same conditions for both. 320z cup, 40/40/20 happy frog/perlite/castings.

Sorry, no ph analysis but using R.O. water.

Thank you for any insight.

Was it colder outside…?
Ps doesn’t look like light or heat issue… But I’m no pro on cannabis diagnostic

No, just in the day time 65 degree ish.

It’s just weird that the others don’t look like it. It started out “normal” looking.

Thanks for chiming in @Nicky!

1 Like

I would say that is a ph or feed issue not light burn do you have a ph meter if not you definitely need to get one ro water take everything out of it so you will have to supplement the calcium and other minerals. I seem to always get a weird one to were every body looks good till you get that one that makes you say what the hell. I have flushed and used comeback from fox farm and good results with it. Your nitrogen may be higher in this cup to with the worm casting probably just enough to make it act funny but im not 100% sure on that. Everything thing else looking really good though


Yeah I would. Agree definitely want to know the PH although tap water Ph’d will do fine if done correctly.

Weak genetics… If your doing the same to everything else? Idk I’m just swinging here but definitely PH water

I bought a fancy Milwaukee meter that does TDS and EC as well with s probe for soil. It will be here in a couple days.

I’ll report back!

1 Like

Just a little nitrogen toxicity, the leaves are starting to claw. Probably just the hot soil you’re in. Give her a few more weeks, and if she doesn’t straighten out, you can flush her. I’m betting she will be just fine, just keep an eye on her. @AAA


Thanks @Covertgrower!

I didn’t think castings could be too hot.

1 Like

Got my fancy PPM/PH meter today.

Check my tap water:

8.3 PH/ 920 ppm

Check my R.O. water:

8.2 PH/ 850 ppm

Paid a friend who is an HVAC guy, but also does water heaters to install the R.O. system.

After further investigation he forgot to install the R.O. membrane in the main canister.

Had to water the NL plants with the alleged light burn yesterday. I did so with the R.O. water confident that it’s good.

Yep, still got the problem, just the one though!

Sooooo did you test the RO after it was fixed?

jiust checked.

80 PPM

PH 9.2

PH went up? I was expecting down? Thoughts?

You sure your meter is calibrated? 920 ppm is approaching unsuitable for human consumption.


Yeah so thing is off… What meter are you using? If it’s anything cheaper than an apera ph20 your wasting your money and time… Gotta spend a acceptable amount on meters

It’s calibrated.

1 Like

And actually I think the R.O. was 920 and tap 850. There were some solids in the canister that should have had the R.O. membrane.

As stated above it’s at 80 PPM now. I still need to run it some more.

And thank you for the feedback!

Okay 80 ppm out of the RO and it’s 9+ PH…
Holy crap.

Drinking water federal standards.
TDS level as follows: excellent, less than 300 mg/L; good, between 300 and 600 mg/L; fair, between 600 and 900 mg/L; poor, between 900 and 1200 mg/L; and unacceptable, greater than 1200 mg/L
pH isn’t a quality that falls under EPA regulation because it’s considered an aesthetic quality of water. However, the agency recommends that municipal drinking water suppliers keep their water supply at a pH of 6.5 to 8.5.

My tap is 270-350, and 7.4-8

It’s not really a pH of 9. RO water and distilled water are too clean to get an accurate pH reading from, and it will always read high with pure water. You can add some pH down (just a few drops and it will likely drop way down into the 5’s) and then start adding pH up to bring it back up to a proper range. Mostly what you are doing is adding substance to the water for the pH meter to read.
I prefer to speed this process up a bit by adding 1 part tap water to 3 parts RO water - then there is already something for the pH meter to read and I spend less time adjusting.


Did you remember to flush it (I forget, but it’s like 30 or 60 minutes) after you installed it?

@AAA when using RO water, don’t forget to re-add calmag back into the water. The RO membrane removes everything but the water. :wink: