What are you seeing leak? What color is the wetness? Is it covering the shoes? Do you have pedal fade (goes to floor) or other hydraulic brake issues?
The reason I ask is because I wonder if you might have an axle seal leaking oil onto the brakes.
As to the brake system - inside the brake drum, the only thing that has brake fluid is the wheel cylinder, which you state you replaced. If you replaced it and you still have brake fluid leaking from that wheel, then you may have a faulty new wheel cylinder.