Late to this party, but remember my experience with ceramic pads and they are hard and prone to squeal.
Personally I prefer softer pads.
Did you disassemble your rear master ?
Did you try to poke a small hole inside to make sure is unblocked as RBM suggested ?
Hi, don't worry, my brakes are playing up still, I just moved on to other things for now.
I am not sure, if ceramic pads in general, blue Brembos or my set in particular is really bad at stopping the bike whilst wet, but these are. Actually I have to lean on the front lever pretty hard for it to stop the bike the same way, as a two-finger operation would, whilst dry. I have just noticed with the dried on salty road grime on the rotors, that right side caliper works unevenly, as the outside of the rotor is nice and shiny, the inside is shiny in the central part, but fully dull and dirty on the outside parts, where the pads should have cleaned them.
Rear MC wise - I have cleaned the cylinder as well as I could poking things through holes and checking for cleanliness, but I must have done a bad job, as the rear brake is just as sticky, as it was before...