[Closed] Leaking shaimano SLX brakes?

Have a set of 2012 SLX brakes fitted to the commuter bike, which gets used 4 times a week rain or shine. After about 2 months use, they appear to lose power untill i get a lot of heat in them, then they are fine again untill i use the bike for the next commute, where i have to repeat the burn in process. I've changed the pads, same thing. Last night as i hosed the bike down, with the water pointed at the calipers i noticed an oily slick coming from the caliper. Bit of searching on the web showed that this is not an unheard of problem, but which seal is likely to have gone? It appears to be both calipers, front one less than the rear though.