Jess, I agree with LoveMaltese's advice. What has happened is, when you change a dog's diet AT ALL, even if it's just a diff kind of same brand food, you have to introduce it slowly, by, for example, mixing 1/4 of the new stuff mixed with the old stuff for a couple days, again for a couple more, until the change is complete.
The lamb bones MIGHT make things clog up, and explains the yelp your dog gave out when you touched his tummy... could be the bones are just laying there and touching that spot hurts.
Your vet will take care of everything. They will need, as LoveMaltese said, something for their gas! What a great insight into your dogs' condition. We, as humans, take stuff like Tums to release gas, or a bubbly drink, and other bottles of stuff in the drugstore to stop bloating, stomach pain, and so forth. Your vet MIGHT want to keep them for a couple days, to make sure the lamb bones pass... he may have to use an endoscope (they sedate and then put a little tube into their mouths, work it down to the stomach, and grab out the bones,if needed).
Just remember, no bones of any kind except big, hard, strictly chewing nylon ones from the pet store. And also, anytime you introduce a new food, mix it a little at a time to their regular food, more and more over a period of about a week, until it is ALL new stuff. That should make it much easier for the dog's body to be able to accept new foods.
Let us know what the vet does! I will be thinking of you and your pups and hoping for what I know will be an excellent outcome!
It sounds like bloat caused from the change in their diets...from ingredients like corn, wheat, rice, soy and oatmeal. These carbs are highly fermentable, and fermentation produces gas. This can be very dangerous if the dog's stomach twists, I would avoid that new food all together and call your vet for what treatment is necessary.