My upstairs master bath toilet leaks at the base. The leak is at the rear left, under the valve. The leak is not clear water, it is brownish water. If I feel around the valve and tubing running my hand up to the toilet there is nothing wet, therefore it is not the valve or inlet tubing. No other toilets in my house leak and I have no slow drains in my house. Since this toilet is on the upstairs master bath, it is not the lowest point (pointing to a main line backup). When I moved in had it re-seated twice times by a professional plumber. Then I had a plumber install a new toilet (I broke the previous toilet's tank). The new toilet leaks too. Both toilets were stable and not rocking. The toilet flushes fine and clears the toilet with one flush. Also, it rarely clogs. Any ideas?