Looks about the same way my skimmer sock does after it's been in for a few days. If it's happening quickly, your water could just be dirtier than you realize (and your skimmer sock is doing its job). But I don't know that there's anything correlative with your cyanuric acid. If there is, I suppose because adding the CYA would make your chlorine more effective at killing organisms because it helps maintain your levels against UV degradation, you could have more shedding of dead organisms and so your sock is getting dirtier faster, but eh...that's not a theory I'd really get behind...just spitballing. Either way, I don't think it has a directly causal relationship to the CYA in your skimmer.