Can dogs get the flu?

[highhoney36]

HEllo I have a female golden retriever black lab cross who is almost 2. Last week I introduced a new dog food to my dogs, I have 3. The older dog did not eat this new food but the other 2 did and they got diarhea, I fed them Lamb and Rice. The one dog had diarhea for 3 days now she is all better but my other dog still has diarhea. and today she is not walking well at all, she is eating and drinking fine and she seems to be happy but quite lazy. I am wondering if it was the food I fed them( which I changed back to their regular food)or if they might have the flu. Her stools have no mucas or blood or worms. but it is very runny. Also I am wondering if maybe she is not moving to qucik because her but is sore. I live in a small town and the vet is 2 hours away. I am waiting for her to call me back so id anybody has any thoughts please let me know. Thanx alot.