El your starving them. I just looked up the feeding schedule from GH and Floranova at this time should be 7.5ml per gal, roughly 1 1/2 tsp per gal. You are getting yellow because they are crying for Nitrogen. http://www.genhydro.com/genhydro_US/...ainToWaste.pdf There is the link to feeding schedule :thumbsup:
Calmag is still a good idea even if you dont have a problem. The label of the GH version says 5ml per gal (1 tsp) but I am running it as a preventer at a little less than half that.