I have noticed that pitchers such as Ashby, Megill, or back when Devon Williams was pitching for the Brewers, they were less reliable pitching on the second day of back-to-back games. I don't know if Ashby warms up differently in the bullpen that causes him to be less reliable on the second day. It also depends on how they are told to warm up. There could be "get loose," "start getting warm," and "get hot." They are all contributing factors.
Even so, Ashby can be lights out, but when he falls, he falls hard.