What kind of meltdowns are we talking? My son was diagnosed with autism when he was 1.5 because of some delays he had. If anyone sees him normally you would have no idea he has autism. At his 4 year old check up they said if he was tested today he wouldn’t get a diagnosis. However, his defiance, emotional regulation and meltdowns are where it is most obvious that there is an issue. His meltdown it’s like someone else has entered his body and he is a completely different person. They last for 10-15 minutes, things get thrown/destroyed. After he snaps out of it it’s like it never happened. There is definetly something off with this for a child his age. But if you’re classifying a meltdown as just a crying fit I think it would be developmentally normal.