Battery life on Watch series 5 sudden drop to about 3 hours

My Watch 5 (MWR42B/A Cellular ,global 44mm) running watchOS 9.3.1 has just started to have a battery life of 3 hours. I have done all the usual stuff, reseting, unpairing and repairing update software on iPhone, etc. and it still has to be charge 4 time a day.

Help! what do I do next?

Thanks