What exactly causes frazzle top and how can it be corrected?

I have a Queen Palm and 2 noid fan palms and they are all showing signs of frazzle top on the fronds. I first thought it was due to grasshoppers chewing the fronds up but even the new growth is frazzled. They are planted in pots as they do have to overwinter in the house and have been fertilized with the same fert I use for the citrus(slow release with minors). Is there sonething I'm missing. The frazzle top started about a month ago and appears to be getting worse.
Andi

Epsom salt (Magnesium Sulfate) usually corrects this. I use heavy doses of Epsom salt on all my palms and they rarely show any signs of deficiencies.

Thanks Laaz. Everything I had read suggested it was a manganese deficiency but the fert has plenty of that so I had to look for another cause. Magnesium was never mentioned. As soon as it cools down a bit I will give them a good dose of Epsom salt. Its too hot right now as its 99° with an index of 115. Too hot for me to be out there but I have a ball joint that must be replaced and all the shops want $600+ to do it for me.
Andi