I have some kefir grains, and they seem to be pretty big. I initially thought this was the kefir growing, but apparently whey is stuck to the kefir or something? I've shaken the bottle fairly rigorously but it won't come off. Any ideas? Am I supposed to separate this "cheese" from the kefir before the next batch? Or do I leave it? If I'm supposed to separate it, how would I go about doing that?