I also agree with Jo and Mike.
The only thing I would like to add is the females when in heat also want to breed madly.
Like Mike said, after females have a litter, a few hours later they go right back into heat and if the female is particularly dominant, may be fighting with the other two females to give herself the best chance of being bred before them.
The male and female in heat are being swarmed by a truckload of different hormones and cues, it can make them do funny things.
They will get it sorted out, one way or another.