This is an auto flower. Seed sprouted July 15. Saw white hairs around aug 15. Not sure if that is technically the beginning of flowering, but that’s my time line. It’s in a 3 gallon pot. Went with ffof and everything has been great. I have a second plant that hit a wall and took a nose dive around the beginning of sept. Feedback I got was calcium deficiency. Add cal mag. I did, to both plants moving forward. Seemed to help the one that was damaged and this one kept growing but seemed to be a couple weeks behind the other. I started adding ff trio with cal mag about 3 weeks or so ago. All good until the past two days. I went a day or two too long between waterings and she was pretty dry. Watered yesterday with cal mag and trio. During watering I noticed the leaf damage. That was about 18 hours ago. So I guess I need to understand if it was letting it go to long without water, or potential salt build up. Maybe nute burn. Probably not light issue.
As of right now. One more thing of note, humidity had been around 70. No issues but was looking to lower so got a dehumidifier and humidity dropped to mid 50s within a couple days
Check your humidity/heat/fan…looks like a VPD issue…
Looks like very dry air…how does the leaves feel to the touch…?
You mostly have nute burn. I didn’t see if you were checking your ph coming out. You need to be sure that your ph in runoff is in proper range. If you have checked ph in runoff what is it coming out at.
Are we talking about the small plant?
Yeah, I didn’t realize some of the responses were about the small plant and it got me off track on who was replying to what. Haha. I now notice the arrow indicating who the response is directed to
The bulldog got you on the big plant…the small plant, check VPD and save yourself future issues…
OK I’m thinking there’s some confusion, it may be mine. Your ph should be going in at 6.3 to 6.8 in soil. If it is coming out below 6.0 then that could be causing some issues. I just went and saw responses you’re coming out at 5.9 . This could be a issue. If you are using FF TRIO and haven’t flushed with something like sledgehammer, you probably have some salt built up in soil. Your ph may be out range in soil. My advice would be to flush with Sledgehammer and properly PHed water. This will help remove salt build up and get ph raised back into proper range. Once you flush go ahead and feed immediately after. Use cal-mag also when you feed. I’m assuming you are writing off the smaller plant. @Arrow was discussing VPD this is important also, try to get environmental issues as close to chart as possible. But you definitely don’t want to have rh to high this far along in flower. Bud rot and mold isn’t any fun to deal with.
@Bulldognuts thanks so much. Yes, ph is coming out at 5.9 and going in at 6.4. I don’t have sledgehammer on hand. Will straight ph’d water flush suffice?
I know that I’ve seen where people have used straight water. Be sure to use your tap water, I think you said it was at 85 ppm. If you use RO water it won’t ph properly. I wanted to mention also for future reference that if you use something like Sledgehammer or similar products always feed immediately after. The Sledgehammer will not only take out salts it will strip out nutrients and beneficial microbes. 
Wanted to also recommend that you remove some of the damaged larger fan leaves, especially at the bottom of plant. This will allow more air flow and possible future rh issues.
Hey sorry bud not trying to hijack your post just have a similar question planted 20 skywalker seeds and 15 have popped two are still tiny tiny seedlings in solo cups the rest have shot off but one has grown light green using fox farm ocean mixed with pro mix organic soil from local nursery currrently under 6 Leon lite 48w 4ft grow lamps any ideas why this one might look this way? Oh and havnt fed any nutes yet planted 9/9 sprouted 9/11-12 using ph tap water at 6.2
I also use the FF trio, but once they flower I stop the Grow Big… in fact, with my soil (Recipe 420), I find I don’t need to use any nutes at all until the TDS out drops below 800-900. Flush is definitely what I would do (Although I am absolutely no expert LOL). I also like Recharge… it helps damaged roots and keeps them healthy. The little bit of purple I see, I found mine was a phosphorus deficiency so I added liquid bone meal.
That could be anything really. I would start with a soil slurry test (for ph at the roots). Google ph slurry test and let us know how it comes out. You’ll want to do it on all the plants (PITA, I know) but that’s the best starting place.