Why don't you post all the levels of all the tests? Sometimes we see something that tells us more. "OK" is pretty vague.

I'm not the expert on SWGs. Waterbear and PoolSean know far more. But I do know that you must run higher CYA levels with SWGs. If CYA is zero, you are going to have troubles. I believe the recommended level is 70-80ppm for CYA.

Have you been losing CYA or just never had any? This is important.