Light burn or nute lockout?

I feel a PH of 7 should not be drastic enough to cause these issues in a soil based grow, soil regulates its PH quite well. To me this looks more like an issue with lighting and they might be to close as that could be why only the tall plant is being affected. If any foliar feeding is being done I would not do that with lights on. Good Luck!

I would have to agree with what someone told you. It looks like a PH issue to me, Especially if you are still at a PH of 7. You want to be in the range of 6-7 so 6.5 is where you want to try to keep it. Being on the top edge of the range you can start to get deficiencies because the plant starts to have trouble up taking nutrients. Like Roberts said. Check the PH of your runoff. If it is not in range then you can start to run into issues. This would also make sense as to why the taller plant is the only one showing it. "Generally" When plants eat more then they drink then the EC/PPM goes down which in turn usually the PH will go up. When they eat less then they drink then the EC/PPM goes up and the PH will go down, A bigger plant will eat more then a smaller plant making the amount of food less. This is a general observation as PH can go up/down for many reasons. Happy Growing

My guess is you've got nute issues because of your pH.... 7 is pretty high, especially in flower and some important nutes aren't readily available to the plant at that pH. You need to get it down to 6.2 as a "sweet spot" in flower.... If you've got a lockout because of your pH, just throwing calmag or dolomite or whatever at her isn't going to do anything... You're going to need to flush her out (3x the pot volume of pH'd water - so if you're growing in a 3 gallon pot, that means 9 gallons of water through her). Test the runoff of that water to make sure you've gotten the pH in the runoff down... Then, after she's dried out from that, you can resume your nutes at 1/2 strength for the first feed. One thing I like to do with my soil grows is to topdress with 1 tablespoon of Langbeinite 0-0-22 once a week throughout the grow... that seems to help completely avoid calcium deficiencies (as long as the pH is controlled) as well as obviously giving a good boost to flowering. Good luck!

Well it can really be both. Have you tested your run off pH? Are you getting decent run off when feeding? Like 30 percent of what you put in comes out. I have a SE3000, and it's a strong light. Mine hangs at top of 5 ft tent always. I run around 30 percent in vegging. Depending on what the plant tells me. You should always test your pH. It can change, and greatly improve your grows.