Ok, this last cory apparently has 9 lives like cats. Last night he kept falling onto his back. Then he would freak out and race to the surface, then he would fall on his back. At one point I was going to get the net and help him towards his final resting place. Instead, I did a 30% water change and thought I'd check back in the morning. This morning, he is upright and just chilling on the heater. I'm at a loss...I think I'll just keep doing water changes and no more gravel upset.