I hate hoof issues more than anything! Hopefully it is something his body is going through that may right itself and he won't have any detrimental effects.
I do agree with the opinion that peroxide isn't the best. If you want to bleach something, sure it's good. But I'd lean away from it for anything animal related. But it looks like you've already decided to do that.
I'll be watching to see if anything changes for you.
Riding: The art of keeping a horse between you and the ground. ~Author Unknown