My Dogs nose is often dry at the top. He has free access to water and is drinking/eating normally. Do any of your Dogs have a dry nose? If so, is there anything that you do to prevent it from getting dry?
A dry and flaky nose is quite normal for many dog breeds. Try using the pup wax from Puppington, it is quite effective for both noses and paws. If the nose doesn't start to heal within a couple of days, then get your dog checked for canine hyperkeratosis. And if your dog's nose starts recovering then there is nothing to worry about as it could be just the weather.