Hi - my LO (also 13 months) went through a stage just like that about 3 weeks ago. He has always eaten well but just started only accepting finger food and anything I spooned in just got spat right back at me.
It was very hard but I just ignored it and gave him a good selection of finger foods to pick at. Actually, he wasnt much interested in them for a bit either so perhaps it was his appatite dropping off. Anyway if he didnt want to eat I didnt make a fuss and I didnt start rummaging through the fridge to find other things to offer. I just made sure that each meal was different textures, colours, things he'd eaten in the past, new things etc etc. He kept it up for about 3 days - only taking little bits here and there at meal times and same at snack times; then went back to normal.
So I'd say - hold out. it could be his teeth, his appatite or something else all together. I think I learned that he is now excersising more of his own choice over things. He's a fairly easy going chap and prior to this he'd pretty much swallow what got spooned in but now he's deciding if he's hungry or not or if he likes the taste / textuer or not. So long as I dont make a fuss he doesnt keep it up for long and I'm learning what he likes (which is still most things at the moment).
I know how frustrating it is as it presses so many buttons!!!
a) you've prepared that food and put in lots of effort
b) its messy
c) its a waste
etc etc
But stay calm and hopefully it will pass.
HTH - let me know how you get on...
xxx