Two watch combo - Losing/Gaining seconds

[mung82]

Hi all,

My first post, so thought I would share a pic of my Rolex combo. But at the same time I seek your advice.

I set these watches at the exact same time, down to the second. Each day the BLNR either gains circa 10 seconds or the YM loses 10 seconds, and as a result you can see I will lose over a minute a week. Both have been on the same watch-winder, BLNR has been serviced recently and YM pretty new.

I had a search, but couldn't quite find what I am looking for. Am I expecting too much or is this something strange?