I looked at the pix, where do you live? I am in SW Fl very near the gulf
and have two queen palms that are doing well. One thing I noticed in your
photos is that there are plants all around the base, along with leaves, and
rich moist soil. This may be the problem. I believe that they tend to like
drier bases, like most trees. So, there may be a problem with rot. Other
folks may be able to diagnose better, I just grow them in my yard! Oh yes,
I also thought of something else - if these were planted as grown trees in a
subdivision, they may not have a good root ball or were improperly planted.
Also I keep my coverings of the bark (the base of the fronds when the fronds
are dead) on the tree, I like the look and they catch more water. Palms are
shallow-rooted grasses. Good luck!

--
gloria - only the iguanas know for sure