Do you think it was the potting mix that caused all the plants to die. Seems unlikely to have been a problem with the plants being they were doing well before the repotting.

I think that could definitely have been one the causes. I also think I may have overwatered them. I was so distracted by other things going on that I was just not really tuned into what I was doing. Next year will hopefully be better. I really want to grow those PP's!