WH-1000XM5 Battery Draining whilst off?

Purchased maybe 2 years ago now and have been working perfectly since. Problem started a month or so.

Put headphones on even if they was charged the last time i used them the day before to greeting of ‘low battery’ and then turn off 5 mins later.

Go home and charge them and ensure i turn the headphones off after not using even though the setting for them auto turning off is on.

They may hold charge for a couple of days then it happens again with the battery being flat.

Use them for about 2 hours a day for the gym and walking the dog but if i remember correctly when i first got them i could go weeks without charging them.

Is this a new battery job?