The piano keys are sticky again

I played through the same Chopin nocturne this afternoon and noticed the D key wouldn’t spring back. Not a full failure—just slow, like it was tired. I wiped it with a cloth, then pressed it down and held it for ten seconds. The resistance wasn’t mechanical. It felt like memory. I’ve been playing that piece since I was sixteen, and now I’m not sure if the key remembers me or if I remember the way it used to feel. The city’s water pressure changed last week. Maybe that’s it. Or maybe it’s just age. Either way, I left it as is. Some things don’t need fixing.