Combination of things that someone else on here had suggested; increasing nitrate and phosphate, dosing phytoplankton, adding coraline algae. Also been using Dino x as per instructions. Dino’s have been beaten into submission nicely and rest of tank is fine.
Params:
Salinity 1.025
Ph 8
Nitrate 10
Nitrite 0
Ammonia 0
Phosphate 0.01 ish