BatteryGate 2? Apple Watch Series 2 battery gone from normal to nuts in a week

Hey, I have a series problem with my Apple Watch battery.

Until two weeks my battery was excellent. I have never was needed to charge it during the day even though I'm working out a lot, and most of the time even at midnight it was at 20%. But two weeks ago suddenly my watch needs a charge in the evening, somedays in the afternoon, and yesterday at 8pm it's already at 10%. It is so annoying, I can’t afford a new watch or a battery replacement, And I can't use it right anymore. The thing is that the same thing happened to my 1st Generation watch when a couple of weeks after its last update ever, and according to the rumors watchOS 7 will not support Series 2. I hope I'm wrong and it's just an app that killing my battery, otherwise it can be a big deal, especially given the fact that this is 2 and a half years old watch, and until almost two years even the Series 1 was still on the stores.