Stuff in brake fluid?

my brake fluid looks dark and its got black crap floating in it. this is only in the front brake reservoir (the big one) Obviously this is an issue. But what is the issue do you think?

Heres the "history" of the brakes. 7? years ago my dad rebuilt one side of the suspension and put a new caliper, pads,rotor and rubber line on that side. The car sat for 5 years. 1-2 years ago i rebuilt the other side and put a new caliper on, pads,rotor and rubber line. I put a new rear rubber line on and new hard lines on the car as well and obviously added fresh fluid. Last year i put on a new booster, master cylinder, wheel cylinders, drums and rear pads. I must have bled half a gallon of fluid threw the lines and the pedal was still soft. drove the car around a bit, and now i have this fluid issue. Probably related.

So what should i check and do? I'm rather P.O.ed after replacing all that stuff and having issues still.

Yes i do know how to bleed brakes, done a few and never had issues. And yes the front calipers are on the correct sides with the bleeders at the topmost part of the caliper.

any help here is GREATLY appreciated!