I have a 4 yr old boxer . I have bred her twice the first time only 2 pups the second 0. This time she came into to season and everything was looking fine; we did 4 breedings 10, 11, 12, and 13 day. On the 15 day she started showing color and was flagging again. I have been wondering if this could be a split heat. I have heard of that but never experienced it before.