Unlikely, firmware updates do not normally change any power output settings and that is the only thing that can affect range if nothing else has changed.
You can check the power is set to maximum via the router dashboard.
Have you moved the router at all ?
Is your line-of-sight to the router now affected by plants or trees that have recently come into leaf ?
I had "vegetation" issues at my overseas property and had to resort to the big chopper.
