It’s not your job to read minds. It is your job to read faces once in a while.

There are two different standards here and only one of them is fair. Nobody can be expected to work out what somebody has decided not to say, and feeling guilty for missing a hint that was never given is a waste of a week. What is reasonable is noticing the obvious: the face that has gone still, the person who has stopped joining in.

So drop the mind-reading and keep the looking. Once in a conversation, lift your eyes and check how the other person is actually doing. If something looks off, say so plainly and let them answer or not, which is the whole of your job.