Did the yellowing start in the older leaves or the newer ones?
Ok I'm going to test the nitrates this morning. The basil is yellow in its stems and leafs. The mint seems to be much greener, and the parsley has some yellow leaves. I will post the results after I do the test. Thanks for the advice!
Roland, Just my two cents. My system was at a high pH for several weeks when it was cycling and now stabilizes around 6.6-6.8. I too have very hard water. I would watch adding pH Down from Pet stores as some of what they sell has sodium in it. I had to order mine online as I could not get the pH Down for Hydroponics locally. Even when I added it, it only held the pH down for a day or 2 and then it would go back up. I think you will be fine once you bacterial are established.
Roland, magnesium is commonly added in the form of magnesium sulfate (epsom salt), which can be added to your water, or used as a foliar spray on your plants. Iron-chelate is used to supplement iron (which also is added to your system water).
Hey thanks Guys!
Rob, when you say add iron and magnesium, are you saying that this comes in a liquid and I should add it to the tank or sump water?
For Chris, growstones are made of recycled glass which is why I chose it, as I feel it is environmentally less of an impact than expanded clay pellets which are mined.