Weeping nipples on 996

[Hugh Smith]

Anybody any ideas?I've just returned from Germany 2500miles and have noticed that all 4 brake nipples are moist.I thought it must be just water so washed them off with soapy water , rinsed and left.Master cylinder is if anything over full. Noticed definite weeping again this morning.Would point out that had new discs and pads front and rear fitted less than 4000miles ago.All parts were supplied by Malton and fitted by a trusted independent mechanic who used to work on my rally cars.Have to say pedal feels spongy first thing,but ok after a few miles.I have booked car in for check,suggesting poss.sticking pistons,removal, cleaning of pads and fluid change.Is it poss to build enough pressure up to cause weeping?Must admit am fairly concerned.Anybody had similar experience to point in right direction?