14 gallon biocube upgraded to 5 watts / gallon compact FB, plenty of current with added nano pump, temp 76- 80 degrees, SG 1.024-1.025, nitrates 0-5, pH currently 8.0 (working on getting it up),calcium 400-410, 1.5 gallon water changes w/ distilled water every 3-4 days- I have multiple frags that I have added over the past 6 weeks ( tank is 8 months old)- frogspawn, torch, green finger , and candy cane frags all look great, a brain frag looks good but a small 1 inch acropora frag recently has lost its "top". Last week I noticed the poylps on the very tip were not coming out and this morning the tip is totally gone leaving a white stub. The rest of the frag looks fine. I dont think I have any thing in the tank that could be eating it- hermits, a few snails, a clown and a goby as well as a BTA. any thoughts? Thanks