Agree with applestar!
When plants are over-watered, they yellow and shrivel a little, unless they get damped off, when the stem pinches in at the base and they just fall over. Then the plant is straight and lies flat on the ground, bent from the base.
When plants wilt from lack of water, they tend to bend over from the top.
But, leaving days go by with out watering tiny seedlings like that sounds like not giving them enough water, unless you really over-filled the tray with water to start with. I water my seedlings usually every morning, just putting a little bit of water in the bottom of the tray. When I check the next day, the water is gone (if not, I don't add more). You want them to stay just damp all the time, not wet and not dry.
Did you moisten the soil well before planting in it? Without doing that, the peat can repel water, like a dry sponge does.