Problems with Time Machine

I'm running 10.10.3 and having problems with Time Machine. I have three external hard drives. I've always had the last two of them back up to the first. but now I show all three as "excluded" from a backup and I cannot delete them from the exclusion window (under options.) What's even maddening (but perhaps not a Time Machine problem) is that in the past, the drives have suddenly renamed themselves, and every so often I get notices that there was an attempt to improperly eject all three (they are daisy-chained.) Finally, when TM does backup, the hands on the clock face in the status bar no longer move backward. Does anyone have any clues? Any advice will be sorely appreciated.