Beginner troubles
 

Hello, I started a Hydroponic garden with my father about a month ago and although it seemed simple enough we ran into quite a bit of trouble regarding out plants (mixed lettuce, jalapeno chilies and tomatoes).
http://i1109.photobucket.com/albums/...ps58d83692.jpg


Our lettuce seems to be growing the best, but has slight discoloration on the leafs.
http://i1109.photobucket.com/albums/...ps5257c252.jpg

Some plants have some completely dead leafs among leafs that are growing fine.
http://i1109.photobucket.com/albums/...ps68d0a19a.jpg

We have been struggling somewhat with the Ph balance in our system so Im not sure if thats all that is wrong or if there are other factors contributing to it all. Among the problems with the lettuce our chili plants have not grown much even though their roots seem to be growing.

Thanks for the help