Sometimes adding a fertilizer without prescription will do more harm than good........
Palms like a Fe/Mn ratio in favor of Mn.
Check the bag of fert you used to see if it had higher % of Fe than Mn...That could make the Mn less available and cause more issues. Then you would use a fert specific to Palms in favor of the Micro Mn.
Check with your local University or Cooperative Ext.
Can be confirmed with some soil and tissue testing as well.