Planted Tank Guru
Join Date: Jul 2010
Location: British Columbia, Canada
Quite frankly, I don't see much wrong with your discus set-up. Your tank looks clean & well maintained - and your discus look just fine. It appears your tank is low-tech, with a little algae on the Anubias - but that's to be expected, given their slow growth.
Lighting intensity is just fine, as is the lighting period.
As Hedgefund has said, use more Excel, more often, or hydrogen peroxide (H202) - try dosing either one unto the affected areas at close range using a syringe or test kit pipette, which should help.
But overall, consider yourself fortunate - looks a hell of a lot better than many discus tanks I've seen !