Hello

I have a brand new Sage SGP and a year old GCP. I have always ground beans on SGP 4 or 3 (burr setting at factory level) and pulled 17g to 34g espresso in 25-30 seconds with about one month-old roasted beans from a local place. Suddenly overnight the shots were coming out in 10-15 seconds. Now on SGP grind 1 it is about 15 seconds and I cannot seem to slow it down any more. I have tried tamping hard, light, it makes no difference. I use a purpose built WDT tool with 3d printer needles, a leveller and a tamp with usually high force and never had a problem until recently. Any suggestions? I am cautious about adjusting the internal burr setting on the SGP considering it is two months old now. Thank you

Assuming you haven't hacked the Gaggia Classic, I would assume a chunk of dirt or bad bean in the grinder - pull the burrs and clean/vacuum it and see.

Obligatory advice - use beans less than 2 weeks from roast date for best taste.
edit please spell machine/grinder names out as I had to google to find out what they were. I used to abbreviate things!

Having used the internal grinder on a Barista Pro which is very similar to the SGP, I would not be concerned about adjusting the upper burr assuming there isn't anything wrong with the grinder. I adjusted mine very early in the process and if you read enough posts on this site, you'll see some folks have adjusted theirs almost immediately.