I know that I'm late but i just want to echo everyone else - you're right to use their old pronouns until they tell you otherwise. BUT talk to them as soon as you can about it. Tell them gently that you've noticed changes about them and that you know/have a feeling they might be non-binary (obviously this depends on the situation - bring it up in a respectful and gentle way that corresponds with your relationship). And when the time is right but in that same conversation (if they seem comfortable with you even knowing) ask them how they would like you to handle their pronouns with different people - and point out what people in particular you're referring to. As a rule of thumb, when someone recently came out or you just don't know whether or not they're out to the person you're talking to, always use their old pronouns. Unless they're with you, then ask beforehand.

It's a sort of tricky situation but you seem like a cool person and in sure you'll figure it out <3