Infection on Dog's Gums

First post here - We have 5 dogs. The youngest female developed these small pus pockets (looked like pimples) on the flap of her mouth and on the gums. Hers have grown to the point where they now look like tulips or something. They do not hurt her, but they are communicable since 2 of the other 4 have now got the same. Do dogs get herpes - cold sores, trenchmouth, etc? We can't get to the vet until he is back next week. What are we dealing with here? Anyone else who has seen this on their dogs? I am stymied. Thank y'all.