My 5 year old male English Setter is losing claws, the vet has had to remove three claws in the last six weeks.  He is being treated for fungal infection (enilconazolum soak every three days) and antiseptic (clonazone) soak every day until the lab culture comes back, she said the culture could take up to three weeks and then because of the fact that the infection is in his feet it may be impossible to identify the agent because of all the bacteria and other microbes in the environment.  All claws are now affected with an infection at the underside of the claw at the pad.  All claws (which are all black) have a peculiar line near the middle of the claw.  The claws that have been removed (one each on the left front and both rear paws) have been loose and/or torn nearly off causing bleeding.  A second claw on the left front broke and is out of position (45 degree angle to the pad), but because it is still well attached she did not remove it.  He was treated for 20 days with antibiotics with no result.   Most of his claws are out of proper position, particularly the middle claws on the front paws.  The vet believes he may loose all of his claws, including the dew claws, but certainly will lose at least three more.  She will not remove any claw that is well attached.  She does not believe it is a bacterial infection and although she believes it may be fungal she is puzzled as to why it started in one claw per foot.  She has never seen this problem before and has spoken with several colleagues who are puzzled too.  she is continuing to research the issue.  The dog is eating, drinking and eliminating as usual.
Any suggestions will be welcomed by my vet, me and my dog!

Exactly the same thing happened to our Flatcoated Retriever dog when  he was the same age.  It started off one claw per foot.  We never got to the bottom of it other than it was a fungal thing - however he has grown them all back now.
Becky