Mule palm early diagnosis

[palmluver]

Over the past year, I replaced a row of declining queen palms with these mule palms.  They are putting out new fronds, but I'm noticing that some of the fronds are developing grainy light colored spots.  At times depending on how the sunlight is shining some seem to take on an orange tinge.  Does this seem like a nutritional deficiency or more like some type of fungus? They are getting what I thought was a sufficient application of granular palm fertilizer and even some additional manganese.

[palmluver]

I may have answered my own question.  Found this article discussing potassium deficiency in palms.  It starts with orange tinged spots and progresses to browning at the tips toward the center, which I am also seeing.  I'm going to try some Langbeinite 0-0-22 and hopefully that will stop the progression.