I’m culturing lymphocytes (isolated from whole blood) in RPMI-1640 media supplemented with 10%FBS. After overnight incubation in CO2 incubator at 5% CO2, the media had turned Cloudy and in addition to that there were white threads visible floating in the media ( I assume they were the pmbcs, not sure though). I also observed the flask under inverted microscope but couldn’t understand what had gone wrong. I’m attaching pictures for reference.