Looks like we are having some trouble with the seedlings. After returning from a weekend in NYC, I found that two of my containers has died off in the same way as the cilantro. The cherry tomatoes and the lettuce are pretty much all gone!
I noticed that the dead seedlings are in the same type of container, while the surviving seedlings are in plastic containers. I don't know if this is at the root of the issue. But, hopefully, we will plant this week and try again with the cilantro, cherry tomatoes, and lettuce.