Taking SCARY out of used bikes, one bike at a time.

Yes, it is. It’s from a lot of riding or how often you change those gears. The chain will stretch over time if your grind underload those gears like downshift and crank. If you shift a lot and keep a faster cadence, sometimes that will lengthen the life of the chain.
When a chain stretches, it changes the spacing on your cassette. So the idea is to change the chain out before the cassette is compromised. To keep your drive-train smooth and not damage parts. Change your chain at .5 stretch and switch out your cassette after two chain replacements.
Suppose you don’t have a chain checker tool (and who does, only bike tech). You can use a standard ruler and match pins to inches. Over 12 inches, it should be close, but if it’s off, the chain is most likely stretched, and time to replace it.
Is Chain Stretch Real?
Is Chain Stretch Real?