Please help. My bathtub leaks water from behind the wall and onto the floor (the water leak has caused the tiling to become loose) [I]only[/I] after I shut off the shower. Please advise on a. what is causing this and b. how can I repair it. Thanks!

We just bought a 60+ year old home. It has 2.5 baths(which the fixtures and toliets are original to the home!). There are two toliets on the 1st level, one at each end of the home and one in the basement. All of them seem to have trouble flushing. Most just swirl and never really empty the bowl. It takes 3-4 flushed to get them to flush. Also it takes almost 10-15 minutes for them to fill the back to be able to flush again. We are on cistern water with a well backup. The well seems to be the main supply now for some reason. The well has 2ppm of iron in it. And we have a septic system. The septic was inspected and flushed prior to buying and we were told it all checked out. The piping between the home and the septic was all new 3 years ago. The pipes in the home, most are original cast iron but some pvc. Well the toliets totally clogged one week from moving in the home. We had a plumber come out and they snaked from the outside clean out as well as from the clean out in the basement. The one toliet (on the upstairs) seemed to flush a little better but after 3 flushes it is back to just swirling and not really flushing properly. The other two are not really functional at all it seems. I hope I have given enough info for this. My question is should we just change out the insides of the tank? Should we buy new toliets? Also I saw there were choices between rim jet action flush and vortex siphon flush. Which is better? Any suggestions sure would be appreciated.