Cedar hottub wood fiber disintegration

[Hendrik]

Hi, I have a cedar hottub (Roberts Hot Tub). After about 2-3 months of operation, I started to notice some cellulose, fiber like stuff in the filters seemingly coming from the walls off the tub. I don't think it's biofilm, but rather the wood itself. I heard that (too-) high chlorine levels can cause the wood to disintegrate, but I am definitely on the low side (plus electronic copper ionizer) and also have been measuring cholorine around the <=1ppm mark. My question is, to what extend is this normal or not normal, is it normal at all? Thanks for help.