Introduction and torch issues

Hi, I am new here and have a question about a torch I've had in my 46 gallon reef tank for about a year now. It has slowly been loosing heads over the coarse of a few months now and I am now left with four dead heads and another one on its way. I have other torches sandwiching this one and they are completely fine and healthy looking. All three are in direct lighting with a moderate water flow. Any tips or ideas to help fix this? Thanks.