I have some whey that has been sitting in a jar in my refrigerator for almost 3 months. I was just going to use some today (to make some hibiscus cooler). I noticed that it didn't have the yoghurty/cheesy smell it had before--a very mild version plus a mild metallic smell. There is also a little white filmy stuff in there--similar consistency to "the mother" in apple cider vinegar.
Any thoughts about whether it is usable?