I am so sorry....i live in FL and here we have Buffo toads, I dont know if you have them where you are but I almost lost my lil Mackie to one and the symptoms were almost the same.No foaming at the mouth, nothing except the runs and then she went limp. Also, I read you took them to the beach....my male Duncan got very very sick a couple weeks ago and I almost lost him to bad runs and bloody stools. My vet could not figure it out bc I have him w me always. Then I mentioned he loves to go in the pool w me. We have a salt water pool and he said its very likely the salt water started a chain reaction in Duncan. he felt there was a virus in the water (not effecting humans) and because he was so lil, he couldnt fight it and that turned into hemmoraggic gastritis. It was awful!
I dont know if any of this is helpful but just fyi.
Again, Im so so sorry for your loss. you and your wife will be in my prayers.