*Two year follow up*
After the above posts, the tank took a serious turn for the worst. All SPS died, except for a purple digi that cannot be killed. I should frag that bad boy and call it Extreme Survivor All-Star acro - and make a fortune. Anyway, as things were dying, I continued to buy clean up crews and mexican snails, as the latter eat cotton candy algae (pink fluffy stuff). I replaced all bulbs and checked calibration of all tests. But the crews/snails weren't lasting a long time. Over the last 6 months, hair algae set in, which was a new twist. It appears that the frogspawn was suffering and zoanthids were closing up, either as a result of the hair algae or something else. I still made month carbon changes and monthly 15 gallon water changes.. Alk was at 8.0 and CA was 420ish. Phosphates would fluctuate from .06 to .00. I had been scrubbing HA with toothbrush, but it would reappear in a week.
So I made the drastic change of removing the toadstool leather. It had grown quite a bit and was very happy. The clowns were even spawning in the center of the leather. With the removal of the leather, I did some major cleaning. I aggressively removed all hair algae with a toothbrush. I put sock filters on the return and netted as much debris as possible. I also changed the carbon. And what do you know, all the hair algae is disappearing. After 2 weeks, things look really good.
Despite all this, I was dosing 200 ml of 2 part (alk and ca) via doser, plus 300 ml of saturated kalk...all each day. The coralean algae on the back glass must have been consuming this. In the clean up process, I scraped clean the back of the tank. I think coralean was growing on the back, but it also had a layer of other types of purpleish algae. In the end, numbers climbed and I had to back off on dosing, but only 10 ml.
Observations - The leather was starting to negatively affect (kill) more than SPS. The toxins were hurting the frog spawn and zoanthids. Plus, I think the mexican turbos and other turbos were suffering from the toxin too. As the snails died, hair algae set in.
The leather had a 1 foot diameter. Maybe someone future reefer will want to grow a toadstool leather mixed with SPS and think better of it. Really cool creature, but it will limit its tank mates one way or the other.