Let me be the first to say, that's not a stupid question. A really good one actually. A lot better than someone asking if it's ok to rip farts around their plants...lol. I've never done DWC growing myself, but so long as the plants have adequate water, they should live for at least a couple days. They may go into shock and show signs of stress which you may have to nurse them back from, but they should probably live. Aeroflow setups are easily the most vulnerable to power outages though.