Projectile vomiting help :(

Our little 5.5 month old guy seemed a little bit lethargic today - something was off.. he’s usually really hyper but today he was oddly calm. It was actually really nice he seemed in a great mood all day but just more calm and seemed more tired than normal (he fell asleep on me twice and he hasn’t fallen asleep on me since he was a newborn. Well he ended up blowing out his diaper twice and then later in the day projectile vomited! He’s never vomited like that before so I was super worried! We did spend the day at the beach but it was about 72 degrees F. So not sure if he was overheated or if something else was wrong.. Yesterday we let him eat some apple for the first time though and he went to town on it (BLW). So wondering if his stomach just wasn’t used to it since all he’s been having prior was formula. He seemed ok afterwards but we put him to bed early and I’m going to dream feed to make sure he doesn’t get dehydrated. But it was super scary since we’ve never experienced it before :( Anyone deal with anything like this? Does trying solids ever have this effect?