Although those may test low, maybe they are low because of the GHA. How often are you feeding, and what amount of food? We have had a GHA issue for dang near a year after all the cycles. What we noticed is that it was all tied to feeding and flow. I absolutely added to the flow and that did help, what was causing it was the SO feeding twice a day. I am sure she thought the fish were starving but it is a balancing act. We had to run phosguard to get the phosphates down (25) and manually remove the GHA. We are getting to a better spot now, seeing a difference. Hopefully in a month or two we notice very little GHA.