Might be bad lighting but that test vial looked green to me. I don't use General hydroponics but the 2 different kits I did use Green was 7+ for PH. I needed yellow or light orange for it to be in range. What color does your chart say it should be for the 5.5 - 6.0 range? Also is your water circulated back into your Res? If it is I have a hard time believing your PH holds at proper PH for a week. I run a 1.5 Gallon and 3 Gallon. I used to correct every 2 days but found my plants react better if I correct daily. I have never seen the PH hold for more than a couple days. Not saying you are wrong but these are things I am finding strange. Your temp and humidity is a little bit on the high end compared to me but I don't believe its enough to harm your girls. I'm stuck on this PH thing for now.