Judy,
If you tighten to tight the tank or bowl break, not enough and it leaks.
So you have so far done the right thing and not overtightened.
It sounds like both water closets need additional tightening, be careful and also tighten them even on both sides. If one is tighter than the other it will leak. It may seem easy, but little tricks of the trade may save you from purchasing new water closets. There is no warranty for installing improperly.
Good Luck,
Bill
The Local Plumber
Tustin, California http://www.TheLocalPlumber.com