How old are those plants?
1/8 cup of water is two tablespoons. Did you moisten ALL the soil thoroughly when you planted? 2 Tbsps of water will moisten a little tiny area right where the seedling is, but the roots won't grow where there isn't water, so they can't fill the pot. Yes, you shouldn't overwater, but you could have that seedling trapped in a little pocket of moisture surrounded by a desert.