Do Tannins remove Medications from Water?

I'm treating a sick betta for Velvet Disease (can't even figure out how she got it... I've had her for over a year, she's in a tank by herself, parameters and temps are perfect, and I haven't done anything lately that would cause stress except for a routine water change :irked. My betta tanks are a little more natural, including driftwood and Indian almond leaves because tannins are usually a benefit for bettas. My question: do tannins affect medications for fish diseases? If they remove the meds or make them useless, then I need to change my disease treatment regime.

Thanks a bunch!

Oh, and I'm darn sure it's velvet disease. She has the gold "dust" covering her body, lethargy, clamped fins, and no appetite.