Help! 13 month old lost appetite?

Since last week my son has pretty much been refusing food except for toast, banana pancakes and yoghurt. Today he decided that he doesn’t even want pancakes. I have to persistently try him with those foods before he will start to eat. I just don’t understand as he would eat pretty much everything but now he screws up his face to his favorite meals. I’ve tried offering different meals, spoon fed and finger feeding, even pureeing, I sit and eat with him to encourage him also but nothing is working.

Any ideas???