What could the problem be?

So I went out with my friend last week, i noticed the e-brake doesn't go as high as it used to, and i felt a lot of resistance. After a bit of driving, i noticed the rear left brake (its a drum) was really hot (because the brake pedal sank to the floor). so i stopped at a gas station, and cooled it down with water. I told my dad, and he noticed that the front 2 rims and the rear left rim is really hot. We thought the issue was the master cylinder. we bought one and changed it, its still doing the same thing. It's just confusing how only 3 of the 4 wheels are heating up. What could the issue be because my dad and I are really stuck. The 2 front wheels and the rear left heating up, but the rear right is completely fine.

PS: Front left caliper and rotor were replaced just 2 months ago.

Thanks

What could the problem be?