Compression tests should always be done warm to get the most accurate readings.

I would keep good notes on your findings and recheck #7 after 500 or so miles. If it loosens up again it could be an indication of the camshaft going away. hopefully not

Another option would be to mount a dial indicator and check your lift comparing the readings between cylinders. Again this should be done on a warm motor to make sure the lifters are pumped up. IF a lobe is wearing it will show less lift. I would start with number 7 as that is the suspect cylinder.