A couple of years ago, I asked Andy Easton why some of our Catts had black tipped leaves. He said might be a calcium deficiency. Since then I have added 5 Tums tablets to every 20 gallons of fertilize solution. I start softening the Tums several hours ahead of adding the fertilizer, 15 aspirin, and detergent to the mix. Our black tips are gone, and while the calcium is at best in suspension, the particles seem to some how get into the roots.