Go back to the old food fast. I just lost four puppies. I thought parvo then worms and then ate something nasty. The last was right but it was the food. I went with cheap and the puppies died. The only good thing was that the puppies died and I let a vet look at the last puppy. He could not find any worms at all and without expensive tests he could only guess it was the food. So I threw out the rest before the adult dogs got sick but I found loose poop in the kennels when I came home with new food.
It may not be the food but don't wait just change back and keep looking to see if it is something else. I would shoot them up with antibiodics too. If they are throwing up take the water bowl away and start putting smaller amounts of water in their mouth 15-30 minutes apart depending on how hot it is. If they still throw up you need to inject water under the skin or get them on an IV. Reducing the amount of water at one time may help if they are dehydrated. When dehydrated if you drink too much you throw up and it is worse.
But you are there seeing what is going on. I do a treat everything approach but did not change the food. So I will now add throw all the food out and get new food when dogs start getting sick. Good luck
X2 well said
