Im fighting with some problem on one plant. It sta...

Looking back at your diary I noticed you've increased your nutrients quite a bit according to your logs, do you verify your ECs/PPMs? To me it looks like a combination on nutrient burn and proximity to your lights. Running a 400W HID at 11" to your light I'm assuming your using are Air-cooled system? I'd move your lights slightly up and back off your nutrients to the levels before the tips started to burn. Hope this helps but you are in the final phase of your grow and now less is more as your buds are formed and you are preparing for your flush. You won't get bigger buds at this point no matter how much nutrients you give or the output of your light. You actually want to be on the safe side and preserve your buds and the trichromes. I've seen worse so nothing to panic about, cheers.