Vivoactive 4 batterie draining completely within 5 hours SW 7.8 - bought in Nov 2020

As anyone experienced something like this?  Batterie from 100% to 0% within 5 hours from 1 day to another.  Here are the details:

In the last 2 months, my 3.5 month old vivoactive 4 watch batterie started draining within 3 days instead of the regular 7 to 8 days.  Yesterday, I took it full at 100% and a few hours later I was around the pool sleeping and I suddenly noticed it was off.  I turned it back on and not long after, it turned off again.  I then realized the batterie was empty.  I Plugged it back and once at 100%, I went to bed.  3 hours later it was at 50 %, and this morning totally drained.  

I did not add any new App to it in the last year - I did not change any setting in the last year - Not sure what is suddenly happening.  I have an old vivoactive 1 and the batterie is still good for more than 2 weeks!

What should I do?  Reset the watch to manufacture settings?  What happened to the batterie for suddenly draining so fast?  Can this be repaired?

Please let me know as soon as possible

Garmin please advise