My experience with the PIC18F14K50 and Sleep mode.

First thing I would suggest is to add @NOP right after the @ SLEEP command.
It could be the rascal is not even going to sleep!

Next make any unused pins an output (HIGH). Left floating as inputs was causing erratic higher Sleep currents that varied in the 10's to 100's of uA.

One last thing that really cleaned house before going to sleep was @RESET.
But my routine was structured to power up then go right to sleep until an IOC occurred that woke it up.
After chores were done and activity was quiet for a little and nothing happening.... @RESET... get back to sleep!

And of course the as the guys suggested, all external loads to the PIC need to be considered, they add up.