Ever since I brought him home he has been an incredibly picky eater. At first I thought the bag of kibble (Victor professional all life stages) that was recommended by the breeder was spoiled. I switched him to a different kibble (Inukshuk 26/16) and he started eating well again. At around 4 months old he started to unexpectedly turn his nose up at the kibble. I have tried every: soaking and blending kibble, adding chicken and rice, mixing in wet food, bone broth, pumpkin, yogurt, a laundry list of freeze dried mix ins. Nothing is working longterm. His digestive tract is also so so sensitive. 

He's 21 weeks old now and nothing has changed. I have brought him to the vet and he was put of a course of antibiotics for ongoing tummy troubles and a mild cold and it didn't help at all. He's also fairly picky with treats. He is otherwise happy and healthy.  
I have had 3 other labs from service dog lines and all were great eaters. He is my first field line lab. At this point I am at my whits end with him and the pickiness. 

  just really don't know what to do at this point other than give in and switch his food which would surly case major diarrhea and more sleepless nights of cleaning out his crate. Since he is a working line lab he as a super high metabolism and caloric intake, he should be eating roughly 1800 calories a day. In an ideal world I would love to feed fresh/raw food but I know I wouldn't be able to afford it since he eats just so much. 

Wondering if anyone has had experience with this or has any suggestions? If you have read this far thank you.

I know this sounds strange but my lab doesn't eat.