One of the reasons coraline doesn't grow well, that many people overlook, is the need for good alkalinity levels. Test for this, and adjust accordingly.
Two part additives are only good for maintaining levels, NOT raising them. To raise calcium use Kent's Turbo Calcium, and for your alkalinity use Kents Pro-Buffer dKH. NM Reef was right on. I too drip Kalk, and in addition I use the Pro-Buffer every day/Turbo Calcium whenever my Calcium needs a boost. Since I dropped using the two-parters, and switched to this method, I have had the "coraline explosion", it is virtually everywhere.
I am not a fan of the two-part additives, as I used them for about 8 months with little to no affect. I am much happier with the results from the method I now employ.
HTH
Hermit