Looks like BBA from my view of the photo.
Provide as much of the following as possible, and we can give some guidance. The more info provided, the better we can resond.
- Light (make & model): ideally, PAR and PUR reading at the substrate and photoperiod?
- CO2 setup (if any) and, if you inject CO2, what is the CO2 ppm level and how is it measured?
- Current NO3, PO4, GH, KH, pH and TDS readings and which test kits are used for each?
- What you are dosing (product and quantity) and how often?
- Substrate type and how long has it been in place?
- What is your filter setup?
- Cleaning regimen (filter and water change frequency and amount)?
- Circulation: surface rippling and are all plants gently moving from top to bottom?
- What is your water source and do you use a water softener?