Discovered why my starter wasn't rising...

I went away for a few days with my family and got my father-in-law to babysit my sourdough starters (firm starters from Maggie Glazer's Artisan Baking) while I was gone.  He's a chemist, and said that I had the LID ON TOO TIGHT (I have them in mason jars with lids).  So the reason my starters weren't rising before was because the gas created by the starter couldn't escape, and so pressed down on the dough, preventing it from doing anything.  Apparently, my fil took the lids off and the starters went crazy!

 This is good news - I think I'm going to be set to make my first loaf of sourdough this week!