this is something i have commented on before. years ago when disc brakes were coming into fashion on motorcycles, riders were finding out that when that exposed disc got wet, the pads hydroplane off the disc effectively making the brakes useless for a few moments. if you look at the front disc on most mid to late 70s bikes you will see a solid disc. the bike companies remedied this by drilling holes in the disc to allow water to escape. i have 2 ranchers with the front and rear drums and a foreman with front discs. the ranchers always stop better. i recognize that i don't ride in the same swampy stuff some of you guys do so i don't have the same problems with the drums leaking. if the foreman disc is not drilled, i would look at the possibility of taking them to a machine shop and having, about 3/8 holes drilled along the path that the pads follow. might be the cure. might also ruin your discs.