I'm no expert, but here's my thoughts:
Ok, given your previous readings, I think your water's borderline. Meaning you might be able to work something out w/out adding anything to adjust the hardness.
How's ur nitrates??
How often/much do you do wc's?
Do you add any water other than tap?
Do you have wood in the tank?
Have you had any ammonia readings?
Other than that, let me tell you what I did. I added crushed coral in a mesh bag to the filter medium. The one negative thing I've read about this option (remember there's other options, this is just what I did), is that it can continue to raise the GH value as well. Now, my tap readings being very low on both counts, I haven't had a GH reading over 10deg in the tank and I don't think it's been a problem. My pH has been a steady 7.0 ever since.
I think this could work for you, too. (Your tap isn't as low as mine, but still on the low side.)
I think the area where the elevated GH
may be a problem is with breeding. I know you have molly fry, don't know if that was on purpose or just happened. And I know absolutely nothing on breeding.
If anyone knows any other poss. problems w/ a raise in GH, please step in!
And I'll echo Allie on the med's...ooh..don't...don't...don't doooo that. Too many med's in such a short time!