First I tried the vinegar, did absolutely nothing.
Next was a tile and grout cleaner containing diluted acid. This stuff made the tiles so slippery I almost fell over. Also, and I freaked out when this happened, it bought out the soap scum that wasn't even visible before....not happy Jan. So now I had some white tiles same as you Southies.
Got out my trusty White King foam bleach and sprayed all over the floor tiles and worked it in with a rubber broom. Left for 5 mins and rinsed. White tiles still there. Sprayed only white soap scum tiles with foam bleach and scrubbed with a scourer and then with a magic eraser which has a pink side on it for harder cleaning : soap scum ALL GONE!!!!!!