I am sorry to hear your dogs have diarrhea. My name is Rebecca. I am a veterinarian and will do my best to help.
Could they have eaten anything at the groomer that started the diarrhea?
Where they directly exposed to dogs at the groomer or share water bowls that could have spread infection or parasites?
I would start them on probiotics (beneficial bacterial supplements) such as Fortiflora, Proviable, Culturelle. I would also take a stool sample of the diarrhea to your veterinarian to be examined microscopically for parasites and worms.
If the probiotics do not help, I would next start them on metronidazole, which in addition to being an antibiotic, has an anti inflammatory effect on the colon lining.
If they are eating normally, try a bland diet such as boiled chicken and rice.
Let me know if this helps, and what other questions I can answer.