yellowing seedlings

Hey guys, practicing germinating and getting seedlings going with bag seed until my order from attitudes comes in. Say hello, to big boy, kurly, and Larry. The first two named after what their taproots looked like, there was also a Mo, but him and big boy took a dive from the window sill (doh!). I would assume that trauma caused the yellowing, but of my two yellow plants only 1 fell, the other hasn't had any such traumas (kurly) other than having a curled taproot, and is now still following the curved shape apparently..
Here are the 3

I kept them a little over saturated with water the first few days, I've let them dry out the last two I'll probably water again tonight. Could that be the problem? Is that what's probably causing my yellowing? I know my light is good, its pretty reliable I call it the sun, so I don't think that's my problem.

Still looks really wet, are there drainage holes in the bottom of the cup?

Nope. I was thinking about putting some in, I'm def gonna do that before I get my good seeds. It took two days for the soil to get that dry; I was gonna water them tonight but the soil still isn't bone dry so I'm gonna wait til morning, I'm hoping the water was the problem and that they'll bounce back tomorrow after getting back to normal moisture levels.

A day in the sun did wonders for them, tho. I repositioned curly up to his cotyledons and straightened him out a little, hopefully he keeps going that way. Big boy is way greener, still a slight blemish on the leaf but he should be fine. Larry is still going strong.