high alk

A couple of weeks ago I was heading off to buy some new coral for my 50 gal reef so I decided to test my water params to make sure everything was ok. I tested and the calcium was high (540) but everything else was ok. Well it kinda worried me at first and in the end I just ended up buying a starfish. The next day the starfish was dead, legs everywhere! So I retested the water and everything was still in the parameters of good except the calcium, which was still high. So I had a busy week at work and didn't worry much about the tank until the next weekend when I found a coral I really wanted. This time I took some water into the lfs and everything was good except the alkalenity was at 12.2. I passed on the coral and bought a new alk kit and tested both kits. One read 12.4 and my old one 8.8. so knowing what happened to my starfish and the cal numbers I am guessing the new kit is right and the old one is going to the junk. My question now is is there anything I can do to lower the alk other then water changes? I was dosing with c-balance twice a week and have stopped that to see if that will help and have done a couple of 5 gal. water changes with distilled water, but the numbers are only down to 12. I don't want to go with a drastic water change due to the corals and clam, they seem to be doing ok right now. Or should I just keep chipping away at with water changes every couple of days?

I don't think so, I know they tested nitrates, am, and ph and the alk was the only thing they mentioned as being a problem. I should try my calcium kit on my other tank to see what it reads. I know its been high for the last month (which I'm assuming would be one of the reasons for the massive outbreak of coraline algae in a tank that had little of it over the 3 years it has been set up). I'm heading in there today (when they open in 10 hrs), maybe I'll have them check the calcium for me as well.