1. What is your water source?
2. Have you tested for PO4
3. How long are you running the lights?
All of these could be contributing. Hopefully using RO
water to mix SW
could be present especially in not using RO
water. Lights probably only needed 8-10 hrs a day.
Temp really won't play that big a deal in Algea growth. 76-80 degrees is a good range IMO
. Most important thing is to try and keep it constant.
Otherwise it is not uncommon to a lesser degree. I usually have to use my magnetic scrapper every few days to remove light spots of green and brown algea.