There is a palm disease going around called "bronzing disease" that is killing palms in Florida, especially Sabal palms. It also affects others but I don't know if yours is affected. If you search "lethal bronzing disease palms" online you will find lots of info. I sent an email to my county extension office concerning some sabal palms near my house and I described where they were and what they looked like and they replied back that they knew exactly which ones I was speaking of and that they had that disease. There is no cure. The best thing is to destroy the plant. The only thing you can do to keep palms from getting it is to hire a tree doctor to innoculate the tree every year against the disease and that costs a lot of money.