you should give them bloom nutes from about week 1. all the way through. until 10 days before harvest. and then you want to flush. if you don't flush then the weed can be harsh on the throat :)
That's a classic sign of light bleaching. Which means your lights are too close lol Luckily it only affected the top parts of the flower
Edit: the way to fix this issue is to keep your lights a little bit further away from the plants
they look really happy all i can say is they are going to triple in size when you switch them to flower 12/12 so if you can work out how tall they are now then you can triple that size when it comes to 3 weeks flowering time
forget about the water run off. just concentrate on what's in your watering can. if the ph in your watering can is around 6.5 for soil and 5.8 for coco then you are fine
you haven't screwed up dude, they look really nice. you just gotta keep going. Don't stop. try and keep the leaves from touching each other and keep feeding them :)
Those plants have got Nitrogen toxicity really bad. You need to lay off the nitrogen or whatever you are feeding her. it's going to kill her at this rate.
Lol all those leaves are touching i've just realised. you're going to have to prune some of them leaves at some point or get another fan in there or something because if those leaves are touching each other for long enough you will get PW. (powdery mildew).
Edit: you want to try and spread them...
angle the seedling so it's leaning away from the light and watch it grow towards the light. then turn it around again. keep repeating this method until they get strong enough to support them selves. if it does manage to fall over then you want to prop it up with a tooth pick.
now that you come to mention it. over feeding can cause leaves to yellow like that. so just cut back on the feed a little bit. at this point you want to be using about 3/4 of what it says on the bottle so if it says use 40ml then use about 30ml :)
they look nice a colourful to me, i wouldn't worry about the leaves changing colour like that to be honest it looks really nice. the purples, greens, reds, yellows. it's all apart of the genetics probably. they look like exotic plants