Here's what I think. Looks like BGA a photosynthetic bacteria. BGA tends to find dead spots to colonizes so making sure you have good flow is important. An extra powerhead goes a long way. Your only dosing micro ferts, you need macro's as well. BGA can make its own nitrates, so a lack in macro ferts will give it an advantage over plants. I agree your photo period is too long, especially if your not running CO2. Maybe try 5 to 6 hours? If that was my tank I'd clean clean clean, do a blackout for 3 to 5 days, reevaluate my photo period and CO2, throw in an extra power head, add some macro ferts to my dosing schedule.