6 months ago I moved my gear from a floor level room in my house to the basement. Thats when I started to notice that most of my guitars were sharp when I picked them up. Tonight I witnessed it firsthand. After tuning my guitar, I played it and it sounded sharp on the G and B. I tuned up to pitch again and this time plucked the string a few more times. I actually watched it go sharp on the tuner. :NUTS I think the culprit to be the strings slowly equalisizing the tension fore and aft of the nut. All of my guitars are strung with D'Addario XL .010s. I should mention that all of my guitars are setup for .010s, including nutwork. Other than this strangeness, my guitars are stable and true. Bizzare or what?