
Hi there,
I don't want to be alarmist but depending on how well your vet was able to examine your dog's nose he *may* have missed something - there could be a foreign object like a grass seed, polyp, or even tumour (God forbid) up there and none of these particular instances would necessarily show your dog to be in obvious poor health otherwise :(
Nose bleeds while not unheard of in dogs are not particularly common either - I think I'd be back in touch with my vet asap and let them know that it's happened again. Also if you can think of anything significant that may have caused it initially (such as a trauma) or repeated sneezing (possibly a tiny blood vessel has broken) - anything you can think of that may help reach a diagnosis plus as full a description as possible as to type (consistency and colour for eg) of blood and rough idea to quantity being lost.
Will say a prayer all's well and it is something very minor and easily resolved - please post an update when you can. Best wishes, Teri :)