r/Goldendoodles

My almost 2 year old mini goldendoodle is an extremely picky eater. We have tried many types of kibble (he hates them all) and Raw Instinct frozen beef, Farmers Dog and Just Food For Dogs. He eventually gets sick of all of them and walks away from his bowl, He hates seafood, he won't even eat fresh salmon filet or scrambled eggs. Sometimes I cook ground pork or beef and add it to kibble but if it is too greasy he seems to get a stomach ache. The vet encouraged me to go with tried and true kibble brands but he simply will not eat them. He will go on for days only eating a bite or two. Anyone else gone through this? Advice? He is only 18 lbs and I would love to fatten him up.