those are some sweet looking plants mate, but in some of the photos you posted earlier a few of them where male, (the ones with leaves that look like little hands) and was jw if you pulled them or not, if your plants are yellowing gradually rather than quickly and in patches it might just need a little more light, try lengthening its day a little or bringing the light closer, alot of the time its not a neutrient problem that yellows the leaves, but thats always the first thing people expect it to be....