White tips

It would be enormously helpful to both you AND to us if you had a diary for this grow. We don't even know what it is you're growing - is it an auto? a photo? I CAN tell you that you fed the little ones WAY too early... if these are autoflowers, you shouldn't be giving them ANY nutes for at least 2 weeks and then you would start them with 1/4-1/2 dose to see how they tolerate them. This is easily fixed but the little ones are going to continue to show more and more damage for a couple of days if not a week or more... just give them pH'd water for the next two weeks (make sure the pH is between 6.0 and 6.5) and don't overwater them (overwatering is the state of being constantly wet - let the soil dry out between waterings). The next set of leaves may also show the nute burn but the 3rd set should be looking ok when they come... Less is more - Good luck! Oh - and start a diary! :-D