A week later and my hydroponic plants have grown a little, but not incredibly.Here's a close-up of some red lettuce and a swiss chard in the right corner.
Here's a close-up of a speckled lettuce. Maybe it's speckled trout lettuce, but I can't be sure because it came in a packet of mixed lettuces (Rocky Top Lettuce Mix from Baker Creek Heirloom Seeds).
I picked this red lettuce up out of the tray and there were long roots growing out of the bottom of the solo cup. I guess that's what I made those holes for.