Do 2-3x a week water change, 50% etc, clean off all you can each time, turn lights off for 3 days, disconnect CO2 during this time, add Excel at full lablled rate after each water change.
You may do a daily water change+ Excel+ blackout for 3 days to really beat it back good.
However, you need to really work on CO2...........
DIY CO2+ high nuke light?
Excellent way to culture Rhizo........
You cannot induce it other ways, at least I never have after 15 years.