Toilet Leaks

It WAS a valve leak - got it fixed at the service center. Thanks for your comments!

Intermittent leaks most likely suspect is the 'vacuum breaker'

Small plastic container at top/back of toilet...small hole that gets closed off by flapper when water from valve goes in bottom and then out to toilet bowl.
After flush pedal is closed water drains down, flapper open air enters via small hole stopping any vacuum/siphoning effect.

Sometimes the flapper doesn't close the hole and water leaks out then runs down backside of toilet

It's a Thetford; can't see what model. I flushed it and put paper towel in the back and it didn't leak. It doesn't leak very often, but I'll be sure and have it checked out asap. Thanks for your responses

What make and model of toilet?
My first guess would be water valve.

No! Caulking around the bottom will just keep it in and destroy the floor. The bottom is caulked to keep spills from getting under the toilet - not the other way around.
Since you say it's clear, clean water it isn't leaking from behind the caulk anyway. Anything that comes from BEHIND the caulk is most certainly "dirty".
I would reach around to the back of the toilet where the valves are and see if the connection or something at the valves is leaking.
Also, try to rock the toilet, Does it move? If so then it needs to be removed and have the seal replaced.

What ever the case, get it fixed quickly. Otherwise you are in for major rot and repairs.