Had Kefir go very yeasty, cheesy, and very strong. At room temp started to separate after five hours. I was concerned about the future of my grains.... so tried a drastic solution.
I cultured my Kefir for a week in the fridge at 41F, strained it out, and put the grains in a clean container with the grains and milk. I then put them right back in the fridge for another week to culture. I tried it and it was back in balance...took it out, strained it and placed in a clean container on the counter for twelve hours with new milk. It began to separate...let go a little longer, then strained into a clean container, placed the grains in another clean container with new milk and put back in the fridge for another week. It seems to be right back to normal.
What I believe happened is that the yeast in the grains were overtaking the grains, and the culture process. If I hadn't intervened, the bacteria might have starved to death, or at least been present in some permanently lesser state because the overculturing caused by the yeast in a short period of time would have left less time for the bacteria to culture the Kefir. The yeast thrived less at the lower temps, and allowed the bacteria to regain their foothold.
The moral of the story for me would be that you don't have to throw those grains out when they become too cheesy or yeasty....you might just intervene in a way to give the bacterial components an advantage by adjusting the environment, which will bring the Kefir back into balance. It seemed to work for me.