Yellow/burnt leave tips?

Correct, baby plants need baby feeding. As others have said, at this size/age quarter strength is plenty strong enough. Give her just plain water for 3-4 days before resuming feeding once or twice a week with quarter strength nutrients. Once she has 8-10 nodes, go to feeding more often or go up to half strength, but not both. Also, I would recommend going to 18/6, cannabis can only grow so much during any 24 hour period and growth tops out at 18 hours, meaning you are using your lights for 2 hours each day for very, very little return in actual growth. 18 hours is a scientific fact, arrived at over 80 years of cannabis research and is not a figure arrived at randomly. Another thing, all plants do actually need to "sleep" and any less than 6 hours is just not quite enough for your cannabis plant to undertake her "night time" metabolic processes. These can be likened to - 2 hours to rest, 2 hours to repair and 2 hours to get ready for the next day and this is basically what is occurring during your plants "sleepy time". Any less than 6 hours will take away from your plants ability to do these vital activities. Hope this helps and happy gardening. .... Organoman.

Yea dude, at this point you should be using about 1/4 strength of the bottle instructions. Your EC should be like 0.5-0.7. Get an EC meter. It will save your life.

Definitely looks like it was over fertilized. A slight over feeding will cause just the very tips to burn. In your case much more severe damage occurred. Meaning u were much higher than her tolerable level. A flush and a ph balancing would definitely help. Less is more . Happy growing and stay lit fam.

Looks like too many nutes for such a young plant - I’d flush it and lay off feeding