580C light brown leak from right brake to case

I just got done replacing the Master and Slave Cylinders. I sprayed a lot of brake cleaner and it just rained here. When the brakes are applied the wheels will stop if they are spinning off the ground. I pulled the diff lock cover to free up the diff lock input shaft and found what looks coffee light leaking out of the right brake where it mount to the differential.

I checked the diff oil right away. The oil is good and clean. The brakes haven't been moved in the long time. It also...

580C light brown leak from right brake to case