Pale and yellow leaves could be nitrogen deficiency. Check out link below and scroll way down.

Overwatering could cause yellow leaves. I don't know what to tell you about your drip system. Maybe a moisture meter might help, at least until you can figure your system out.
Then you don't have to bother with it.

Here is a link that might be useful: Nutrient deficiencies

It could also be a manganese or magnesium deficiency...I'd suggest you add one of the timed released pelleted fertilizers according to package directions or water regularly with a liquid fertilizer. Or top the pots off with some worm castings if you can get them.