Starter/Solenoid

I think my starter is dieing or the battery is very low. My lights are nice and bright and the connections on the battery are clean. I replaced my last starter because it started doing the same thing. Could the solenoid be the problem? It turns slow and sounds like it is dragging when the engine is warmed up. When the engine is cold it cranks fine. Well still a bit slow.

If the solenoid is bad then that internal connection could be the problem. Anyway to take the solenoid apart?