What does this sound like to you? Does it sound normal?

So I am a nanny, and also have two of my own kiddos. I have two 4&under I nanny a 3yo. I’m starting to wonder if the boy I nanny has normal behaviors or concerning.

He’s very hard to engage, avoids eye contact, is very passive if toys are taken from him, is very focused when building something/plays quietly by himself majority of the time, is speech delayed (in speech therapy) to where his muscles in his throat/mouth seem underdeveloped the only thing I could compare it to is how severely hearing impaired people may talk, when we go for a walk he goes extremely slow on his bike and looks down nearly the entire time, he doesn’t seem to get excited about much, when I show him/ask him to wash his hands he will just hold his hands there, not moving them, grunts before attempting to use words (though his parents will respond to this so this has worked for communication for him to them), sticks his tongue out almost constantly/hands in mouth, etc. I’m sure there are some things I’m missing but these are things I’ve noticed that seem off to me, I know my son was extra reactive/on the upper side of the developmental normal range, so that’s my primary experience to compare to.

If these are abnormal, how could I address it with the parents? Wouldn’t the speech therapist know better/address it? I’m by no means a professional on child development. Tips? TIA!