@Mike D. I don't want to be teaching grandma to suck eggs, but is the saddle wide enough for your sit bones? I too had been riding bikes for years, but I got saddle sores quite soon after buying a emtb. I never knew what my sit bone width was, but I do now! It seems that my sit bone width was the same as the saddle on my bike, so the edges of the saddle were right where they shouldn't be! The recommendation is that you have the saddle 20-30mm wider than the sit bone gap. (It worked for me).
The WTB "Fit Right" webpage has good advice and a seemingly counter-intuitive method of coming up with your sit bone width from Rachel Atherton. I followed her method and it agreed with my "sit on some corrugated cardboard" method.
Get some single fluted carboard, lay it on a flat surface, then sit on it!
Get off and you will see two depressions made by your bum. Draw a circle around the depressions and then identify the centre of each. Measure the distance between the centres. Job done!
Word of warning: As I discovered when trying to identify the sit bone width of my 10 years old granddaughter, the cardboard method only works if you have a bony arse like me! The last thing I was going to say to my granddaughter was that she had a fat arse, so I blamed the cardboard! So maybe Rachel was being tactful, I will try her method on my granddaughter next time I see her.
Here is a link to the WTB Fit Right page. It follows on with questions about riding style and recommends several saddles.
www.wtb.com