hi
I think you should:
discontinue the rowa phos
check the po4 with the better checker like HANA
if its around 0/04 ppm you should dose phosphate (Neophos by Brightwell)
do 20 % water changes every other day for 3 times
check your RO TDS it should be zero
I checked it with a Hanna checker and it reads .13. Also, I bought an iron test kit and its showing next to nothing, barely readable.

