No, there's nothing wrong with your crows. They are most likely finding a new roost. They are a social and migratory bird and often move their roosting place when necessary. A good roost in a remote location can often hold thousands of birds. Let them move in if you can stand the noise and droppings. They will offer good wing shooting but shoot in their fly path a few miles away and don't disturbe their roosting area. You may have a wing shooting gold mine in a few weeks.