It seems like no matter what I do, cheeses I put in light (8%) brine degrade and get slimy. I've been trying to aim for the correct ph with test strips, have added whey to the brine, added vinegar. Can anyone help me get to the bottom of this? Also, I'm hoping to rescue some slimy feta.
Sounds like you need to add calcium.
Yes I would recommend adding calcium and checking you have the right salt amount by putting a egg shell intact into the brine till it floats.
It is not always a calcium or pH imbalance that causes slimeyness. Sometimes, there are proteolytic, halophilic (salt-loving) yeasts and bacteria that will break up the cheese and cause softness on the surface. At times, the salt itself carries these microorganisms. For example, some halophilic lactobacilli naturally exist in brines, as do halobacter, serratia, and similar species. If what you are doing isn't over, start over with a minimalist approach and eliminate each variable until it works.