I have used PBMCs from patient blood to generate newly reprogrammed iPSC colonies on using Sendai virus, feeder-free method. I obtained colonies with clear boundaries, but cannot see the signature tightly packed cells within the colonies. They look like big clumps. Also, these colonies grow very slowly (although they do grow), compared to the usual proliferative rate of iPSCs. They stained positive for Oct-4 and Nanog. But I am not being able to bank them etc., since they are barely proliferating.

I have attached images of my cells, can anyone identify the problem? Thanks