Planted Tank Guru
Join Date: Jan 2010
Location: Contra Costa CA
Are you adding any plant fertilizer? Read the labels. Do any contain nitrogen in any form?
Do much larger water changes, more often. Try 50% per day, every day.
Get a gravel vac. Not to deep vac, but to skim pretty close to the surface of the substrate. Remove whatever debris there is.
Stop feeding the fish. When you resume, give them only 1/4 as much, and only once every other day.
Aquaclear sponges last for years. Rinse and reuse until it falls apart.