My starter just began to really groan. Everything electrical is working fine in the car. I checked my batteries water and it was pretty low so I filled those back up. It is still groaning and it seems to be getting worse. The battery is 2 years old.

I am going to try a different battery and i'll take a look at the cables sometime this week. Any other ideas besides that? Do starters usually groan and sound like they are having trouble starting when they go bad?

Also I was losing a lot of coolant, but I can see an external leak coming from around the top-middle of the engine block. I do not see any white smoke upon startup.

Low voltage will make the starter groan. If you have access to a voltmeter check the voltage of the battery. You may just need an overnight trickle charge to bring it back.
The other possibility is if the starter is original, the armetuer could be binding or the brushes could be worn out.