What could these spots potentially be, they suddenly appeared in last few weeks before I brought my tree indoors,

Question

Nighttime temps in last month got into low 40s. I fertilized with a nitrogen-heavy fertilizer during summer.

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Answer 1

It is cold damage. These can not handle temperatures that dip into the low 50's. They need to be kept warm, and no lower than normal indoor temperatures.

This article will help with the care of the plant:
https://www.gardeningknowhow.com/houseplants/areca-palm/growing-areca-palm-indoors.htm