I have a few friends who battled the HA monster with water quality like yours.. Any nitrate is food for algaes..
They tried lots of stuff and the only thing that helped them was AZNO3.
They got snails, crabs, new filters for there ro
units cutting lights back, new bulbs and the list goes on and on. After using azno3 it is now gone and their tanks are running good after using it.
If its not every where a few guys used a seahare and they are HA eating fools... Only problem is when the HA is gone they will starve. Guys in my reef club with some hair algae are passing the SH around to keep him alive with a supply of food.
Do you have any mexican turbos? I had a small amount of HA when I set my tank up a and got a few of these big guys and the mowed it down quick