Ds turned 18 months this week. He only started saying mama two weeks ago. He used to say dada but that stopped… he says car but not even sure if he knows what it means. He can’t say anything else and he doesn’t try to either. I thought he had tried to repeat me saying tree but even if he did it wasn’t very close to the word. My niece could say lots of things by now. Should I be looking out for other worrying things regarding development? I don’t think this is normal?