If it's moisture, cleaning with IPA and then allowing to air dry should remove any water
Yes, I was going to try that later. The filters are quite fragile on the Salnote Zero/Zero 2, so I don't think you'd be able to clean them many times without destroying the, but still worth trying if it extends their lifespan.
My Truthear Zeros came with extra sets of filters (maybe just the metal and membrane parts?). I haven't had to change the filters on either my reds or blues, so I don't know if there is foam part in there.