Issue with Rear Brakes
 

Hey Everyone, new to the Mini scene. I need a little help with bouncing ideas on what might be causing my problem. I just got a 06 Mini Cooper really cheap because it needed a few things done to it. One of them was installing new rear brakes. I installed new pads and rotors. Right after that, I left for a cross country trip to and from Oregon. On my way there, the rear hubs were getting so hot, I wasn't able to touch them. Eventually there rear hubs were cooked by the time I got to Oregon. While in Oregon, I installed new pads (Thought I might have picked up too aggressive of pads), new hubs, and new calipers (dust boots were torn and I live where roads are salted). I also checked the e-brake cable and it's good, no binding. By the time I arrived to DC, the rear hubs were cooked again. They are squealing and making the bad bearing hum/rumble.
I thought the issue might have been that I picked up a cheap pair of rotors that didn't have the ventilation between the two braking surfaces. I was looking today and discovered, there is no ventilation on the rear rotors.
So what would be causing my brakes to be ever so slightly engaged that it heats everything up?

Just a thought, maybe the calipers are sticking? It is not uncommon unfortunately.

They've been replaced too. Bought OEM calipers from Mini. The only thing I can think of is that the rotors are not OEM. They are Value Line.