ok so next question. how much should i mix with a gallon of distilled water?
About a tablespoon I think... a little bit too much wont do any harm
Ah right, good good. But yeah, as people have already said, a bit of epsom salts (magnesium sulfate, MgSO4) should do the trick. Chlorophyll contains magnesium, so the reason your plants are turning yellow is probably that there aint enough Mg, so they cant make chlorophyll.
word. thanks for the help i'm about to go buy some epsom salt and more distilled water now.
Sorry, I'm a bit new to everything here, so I have no idea what DWC is... Does that involve water constantly recirculating? If so, that should be fine - just dissolve a tablespoon or two (maybe a bit more) of epsom salts in water, than add that to the water in your system.
Hmm, maybe its some other deficiency then, perhaps trace elements. Does the fertiliser you use contain trace elements or just NPK? I recommend you use a fertiliser which contains trace elements (eg Mo, Mg, Mn, Fe, Zn etc). Most organic matter contains lots of trace elements - I've heard that seaweed (you can buy it at oriental food stores) contains over 60 trace minerals, and blood meal should work equally well.
Hmm, that's strange... How much are you using? Could the problem be that you're using too much, causing nute burn?