That grey/black stuff is what happens when you use salmons when it is wet.One thing about the pics that confuses me - if all the grey/black stuff on the pads is brake dust why isn't it salmon coloured? Maybe your rims could do with a good cleaning - that might improve things.
I just put the same pads on my bike yesterday and, though it was dry, they seemed pretty responsive from the off. I'll wait until the rain catches me before I try them in the wet.
Never had any problems with KoolStop Salmons in the wet, apart from the gunk.