Because it's so hard to find pots/containers that are smaller than solo cups it's common to use them as pots for plantlets. This generally causes no problem and shouldn't with your Petrocosmea either. I would leave them in the solo cups and repot them when they get bigger. At that point you can use a more attractive pot. Right now the plants are getting used to their new growing environment and repotting would be an additional stress. Some people like to repot right away, but I'm not a fan of it.

Mark

Thanks for your reply Mark, I ended up repotting after all - one was bone dry, the other sopping wet. So I am glad i got the conditions evened out. i put them in 2" pots that i cut down to about 1" height. still on the big side, but more controllable. plus, i got a little bonus plant out from under one of them.
Now, how do I tell if they are doing ok? I think they have grown, but it is hard to tell, and the P. Cryptica is still "reaching" - does that mean it needs more light?

Thanks.

Karin