Some people not receiving my text messages

So, the past week or so, I’ve noticed that some people just flat out aren’t receiving any of my messages. For instance: I was in a group chat with 2 iPhone users and 1 android user. Me and one of the other iPhone people weren’t able to see each others messages, but when I messaged him independently, we were able to communicate. I feel like there’s something going on when I’m sending messages to non iPhone people. Anyone have this issue?