It looks like manganese deficiency to me. Palms like plenty of manganese, I've read. Manganese can be less available when the PH gets too high. So, if there's calcium that's been added to the soil, that can raise the PH and be a problem.
I would give it some manganese and maybe some nitrogen, too. The link links to a manganese sulfate product I purchased once. It seemed to be good quality. The link also talks about manganese deficiency in palms (how it's a common problem and how regular application of manganese will benefit palms).