Phoenix Theophrasti Dull Brown leaves

[NBW87 1]

I have a Phoenix Theophrasti houseplant that looks great all winter indoors, but in spring when put outside it turns brownish and the leaves get small black spots.  I don't have it out during freezes.  Any reason for this? I ground planted 2 days ago. I'm hoping it has to do with the fact that it was potted, and it can be better drenched in real ground.   Every spring I have to cut lower fronds off, as they are speckled with black spots.  The room it was in is warm will full sun all winter. 

 

The plan is to protect with thermocubes and xmas lights like my trachy.  In the sun,  my wraps can be 50 to 70 on a bright day.   The fig bed will also be stuffed with cushions and straw.