What exactly are your "minimal" readings? Only reason I ask is that one person's "minimal" might be another person's "OH MY!" And what exactly are your pH and alkalinity numbers?
Reading your previous thread, it sounds like your tank is still cycling, but if your numbers are really near zero, then you may be at the end of it. pH will swing a bit during a cycle, but will calm down in the following weeks.
Your alkalinity is most likely due to the (unnecessary) dosing of PurpleUp. As long as you have a little bit of light, calcium above 360 or 380 or so, and alkalinity between 8 and 12 dkH, you'll get coralline growth... assuming you have some coralline in there to start with. Don't expect to see it overnight, but over the course of 2-3 months, your tank will "purple up" on its own. If you don't have any "starter" coralline, then you can add PurpleUp for eternity and never see it.
Adding supplements before really understanding how they can skew your water parameters is a normal thing when starting out a SW tank. I did it with baking soda to "fix" my pH problem when I started my tank. Once I realized what was going on, I fought my water parameters for months until I got them back to where they should be.
I'd say put away the bottles of stuff, do some research on the calcium/alkalinity balance, and rethink the dosing. Without dosing, normal PWCs will slowly bring your water parameters back in line.
Here are some good articles to start with...
Calcium and Alkalinity by Randy Holmes-Farley - Reefkeeping.com
Chemistry and the Aquarium
... and the absolute BEST article on ca/alk...
Chemistry and the Aquarium