Help 1st time grower having problems

First time grower here having problems wit my plants. Started some seeds from bag and they started off good and one seems to b growing really well but the leaves are turning brown. I keep my ph around 5.5-6.0 and I've tried nutes a few day ago to see if that would help but it didn't only left brown stuff in my res can anyone spot any light on what goin on here?

The small one is growing slow and the roots haven't came thru the rockwool yet the one wit the bigger leaves it roots look good plz help if u can

 

Sry bout posting twice didn't see the first one posted sry and I guess it is tsp damn it well I changed the res to jus straight Ph ro water a couple days ago goin to check on them later hoping they recovered but really not tripping to much over them like I said they are from a bag so it's not like I spent my money on them u kno jus doing these to practice and work my craft and issue out since its my first grow and all but I really appreciate the feedback thank u guys I will post pics here in a few to show what they have done wit the clean water