On the big plant, it just looks like old leaves to me. Doesn't help that the potting mix appears to be DRY.

Now, considering you said you just brought them home from school, it is also possible they are sulking from being put in a new environment, or they got chilled in transport.

To give you better advice though, some more info is needed...

When did you last repot and what potting mix did you use? How do you water? Fertilize? Is the new environment much drier, warmer, colder etc from where they were before? Any glitches moving them? Anything else you did with or notice about them?

Karin

Re big plant: I suggest removing all the old leaves in bottom row or two, and transplanting to new pot ~3 1/2"good luck, marty

looks like cold injury