You are describing three of my colleagues perfectly. Some days, they are friendly, smiling and normal. Other days, they are tired, sulky, won't make eye contact, ignore any pleasantries - just plain juvenile and weird. Staff members just know that is the way they are. I keep being pleasant but others have given up.
That doesn't mean that you are doing a poor job or are bound to get a bad evaluation from them. It just means they are having some sort of strange problem with their mental health or dealing with some crisis that you will never know about. Or it could be arrested development, where they think just because they personally are irritable, folks around them should have to pay!
Every time I see they have a college student to supervise, I always feel sorry for the student teacher. It would be unprofessional of me to warn them, I know. So they have to suffer the uncertainties alone. That said, I always tried to avoid eating lunch and spending all my planning times with my student teacher. Too much togetherness for me. But I always warned them ahead and feel one of my gifts to them was to be myself (chipper

every day.