A few days ago, I strung up my relatively new 2008 American Jazz 5 string with new Dunlop strings. Setup the bass as usual. Nothing fancy, no new gauges or anything. I played the bass for a couple hours that day, then put the bass in the case. 3 days pass. Today, I get the bass from the case, and all the strings are slack. Not the usual new strings, gotta tune up a quarter step because of new strings, but slack. I have tuned the bass back up, and everything seems ok. What happened here?