Your calcium isn't terribly low, and although your alk is on the high end of the range, it is also not out of range. I would think that a water change would fix any imbalances in it.
You mentioned that your duncan has grown quite quite a bit - how closely placed is it to the frogspawn?
Also still wondering about how much attention your clown is paying to the frogspawn. Clowns can try to host just about anything, and if it is trying to host the frogspawn that might be upsetting your coral and causing it to retract. If you don't see your clown paying any attention to the frogspawn during the day, check the tank at night when the lights are out.
Finally, just to verify - have you made any changes to the height of your light, location of powerheads, or added any livestock recently?