Steve, thanks for the great info. I use Kent's pro-plant and sea chem iron supplement. I changed my regimen after I read somewhere else on this site about nitrogen deficiencies. Kent's has 1% Nitogen, which seems to be higher than the rest. You're right though, I have no potassium supplement, so that's next on my list. Just to let you know, my plants don't actually appear to have chlorosis. they look very healthy, but their coloration is just not as dark green as they should be. I don't know if that makes a difference.
Also, none of the fertilizers have phosphates! In fact, many actually say "phosphate free". I've noticed that some people on this site dose with bulk chemicals, but I would worry that I would really mess something up with that. If anyone knows of an easy way to get phosphate into the tank, let me know.
But in reference to your comments Wasser, I dose with iron and Kent's, but unless I double (or triple!) dose, my iron levels and my nitrate levels stay at zero. What is up with that? After the last round of suggestions from the board (about a week ago), I made quite a few changes, so I'm going to see what comes of this. I think perhaps you guys are right, I think there is a nutrient deficiency.
I guess I am getting impatient...how long will it take for these fertilizers to work?
Oh, and Steve, I've heard people talk about Jobe's plant sticks too, and I believe they are just regular garden variety.
Thank you all for your input. This is all great stuff. What it sounds like to me is that there is no hard and fast rule about RO versus tap, but that it's more important to get the right balance of added nutrients not matter what you use.
One last thing...is it possible that I'm leaving my lights on for too long? They usually stay on for 14 hours a day....