For some reason battery life on my series 1 has dropped to just over a day. Standby 1 day, 2 hours. Dropped about eight hours! Usage time 3 hours, 54 minutes with 1% battery remaining.
When you updated, did your iPhone say it was done but the Apple watch, while on the charger, had you type in your passcode, display a pulsing circle that went just over half way around, then reset, before working?