Picky dog or tummy trouble?

I have an 8 month old Anatolian Sheppard puppy who appears to be a picky eater. We have bought him several different types of dog food and he always seems to like them at first but after a couple weeks he completely refuses to eat them. We have tried grain free (actually what we started him on) and regular, expensive and middle range, different flavors. No matter how much he gobbles the food the first time he eats, he always eventually stops eating it.

Even when he is refusing to eat the store bought food, he always seems to eat stuff we give him that's not processed. He loves vegetables (such a weird dog but he get's super excited about pumpkins and cucumbers). So it's not like he is sick but I haven't ruled out some food sensitivity (although it would still be weird because we started with grain free, so it's not grains).

And it's not like he is holding out for better food because we don't give him table scraps and we only give him treats when we are training him, which is not all too often. He is actually not even very interested in treats either but he loves bones.

Any input would be much appreciated!! Thank you!!

Is there any evidence of tummy trouble?

To be honest, if he's able to tolerate well the different foods, I'd just ring the changes and keep his diet varied and interesting

I'm guessing he never finishes a bag. When I fed kibble I had two bags on the go at a time so they got a different flavour each day.

Yes I buy two grain free kibble varieties. I also cook a large pan of vegetable (cabbage, carrot, squash, cucumber, tomato etc., plus herbs), and mix a dollop of that with the kibble and top with a garnish of either raw or wet food..

I would either persevere with a good quality kibble. You could add some lightly boiled beef or lamb mince to make it more appetising. Or you could consider feeding a raw diet.

Or a squirt of salmon oil on the kibble might work.

Thank you all for your inputs!
We did make him some canned homemade food (whole chicken, rice, vegetables) for a while but that proved to be a lot of work and even that he seemed to lose interest in towards the end.
I guess the only evidence of tummy trouble would just be him not eating. I was thinking, since it's only specific foods he refuses, that specific food might make him not feel well.
I think the only reason we ever finish a bag is because the chickens end up eating it before he can lol

I will try feeding him different dry food on different days. I think I'm also going to mix in half a can of wet food at each meal.
I have been avoiding the raw diet because we have mostly chicken available (free) but I don't want to feed him raw chicken because I don't want him eating *live* raw chicken (which he has done but that's another thread...) So we cook the whole chicken until the bone dissolve and he really likes that. Just can't do it everyday...

I don't think you mentioned that it is specific foods he refuses?

Dogs are often very clever and will avoid foods that they sense is bad for them

I think if it was tummy trouble it would show at the rear end.