pads are 105, about 500 miles on them.Or you have cheap and nasty pads on them, possibly.
Then I would say that your 105 brakes are not set correctly.
My bike came with the model up (Shimano Ultegra) and they were utter p1sh in the wet. I've found pads to vary immensely; Koolstops or Swisstop are normally recommended but I found I was getting a month out them; try experimenting.pads are 105, about 500 miles on them.