Sudden onset of desats - can't figure out why

Sudden onset last 4 days in worsening desats.

CPAP pressure still @ 8.6
02 concentrator still @ 2.5L/min

Readings posted here: https://app.box.com/s/bhq2vfl7tzd5jyskp6rs299uwlya7fa8 (dates shown are not accurate; my 02 Ring messes up the date unless I refresh the app after each use).

As you can see, in the first 12 days of the month (and prior) my 02 score was always 9+ - no worries.

Do not notice any disturbances during sleep nor any increase in daytime sleepiness

Mask seal shows ok on myAir app.

I was getting dry mouth on/off, but not during these reduced 02 readings.

Thoughts as to what's causing this sudden drop and whether I should make adjustments to my pressure & my O2 concentration before I see the doc?

If the ring messes up such a basic thing as the dates, I wouldn't trust it.
Get a professional oximeter from your doc and see how you're doing.