I recently sprouted a couple of beans in new cups and forgot to punch any drain/air holes in the cups. Once they got up about an 1.5" + I started keeping them wet because of indoor temps were really high.

These plants did the same thing as yours Sharlson and the only nutes in my soil mix for seedlings was about a 1/4 tablespoon of Bio Tone starter 4-3-3.
I guess the all the overwatering made any nutes available and toasted them, so I cut back all the fan leaves I could and replanted. They came back fine, it just took about 3 weeks.