More water flow maybe, could be BGA on the leaves. Bio wheels are not the best choice for a planted tank. A small canister like a Rena would work well for circulation in a 29G. Do you have co2? Any more info would help.
FWIW, That's what it sounds like to me.I'd bet money that you have diatom algae.
Looks like brown dusty mess that settles on all your surfaces, and easily brushes off with water flow. Generally a new tank issue. I would just be patient.