Share 'Change of Tan'

Here's a question for all of you knowlegable people! I have a bitch who has recently had a litter and despite having a lovely tan, some of the tan on her muzzle has gone black. This has never happened to me before. Is it hormonal? Will it return? Is it from cleaning up after the pups? Look forward to hearing what you think! Great weather here in England, almost too hot for the dogs. Off to the…