20+years of a Cattleya

[Pep]

Good morning everyone- I have been growing the Cattleya that shows in the picture without repotting for a very long time. It was a present more than 20 years ago, and after a few pot changes without dividing, i decided to repot where you see it now.
I have divided the plant several times, but the mother is loosing vigor. This picture is from 2021, know just one or two new growth hold spikes.
I have changed part of the pottting mix (mainly bark with pieces of moss) along the years, but it seems that now i have to change procedure.
Any suggestion?
I keep the plant on a bench in fron of a northeast window, high humidity and no less than 16ºC at night.
Thanks in advance