manderin orange dying

I live in the NYC/NJ area. Three potted manderin oranges were moved in-door in mid Nov. In the past week, noticed leaves drying and falling. No sign of insect bite. Watering once every 10 days. What could be the cause?
Attached is a picture of one of the tree.
Thanks

 

The dried and curled leaves may be the result of exposure to cold temperatures. Have a look at the thread How long does it take for a sick citrus tree to get better? | UBC Botanical Garden Forums and the one it references.

 

Thanks.
The temperature of the room is 62 to 65 F. Will raise the temp and see.

 

I'm thinking the damage was done while the tree was outdoors. Increasing the temperature now will not reverse the damage if that is the case.

 

Thanks.
Will see if it will come back in the spring then