Under 400X magnification, I have "hopping particles" at the bottom of the tissue culture plates. The pH of my media has not significantly changed (It is still pink but is starting to change pink/orange in the past 4 days and the media is definitely not cloudy. Normally I would just thaw new cells, but I am generating knock outs and am near the end of the process. I have read many posts that say it is contamination, discard the cultures, and I have read other posts that say it is precipitate from the serum (I use FBS from Gemini). Any suggestions? Thanks!