First thing this morning my dog was normal.  She ate her breakfast and then had a drink.  As she turned round and opened her mouth I saw a lot of blood on the back of her tongue.  She has been for her morning walk and blood has gone but her gums are really bright red.  The internet search states a serious infection.  I'm phoning vet when they open but how could something like that happen so quickly?  Have any of your dogs ever been like this?

What.does.vet think.?