13 month old now spitting out food

My 13 month old has been pretty good with food, happy to try anything and eats well (he does take a while to finish eating compared to friends babies of the same age but I put that down to being a late teether and only having 6 teeth..maybe?) this past week he has been spitting out his food. He's fine for a while but but after a few mouthsfull, he starts spitting it out. I've tried all different food types, tried feeding him myself and letting him feed himself but it doesn't make a difference..he'll spit it out whatever it is and however he's being fed 🙈

However, he does eat his breakfast (usually wheetabix) and yoghurts without a fuss.

Has anyone else experienced this? Is it just a phase? Teething? Any advice?