Have you tried cutting the solids down a bit at lunch time to see if that makes any difference. He does seem to be eating a lot of food.
Even though your lo does not have any teeth, he can still most definitely be theething. When the teeth are moving in the gums, this can be very painful for them and cause them to go off their food.
I do know that when my DD cut her first tooth about a month ago, she was very fussy on her daytime bottles, but her night time one went down a treat.
My DD is also very nosey as to what is going on in nursery during the day. I have asked nursery to feed her in her bouncy chair facing the other kids, so that she can see what is going on without having to turn her head around. This has helped a lot, and they can usually get her to drink about 6 oz of her 8 oz bottle. Not sure if they have tried this.