One eye shut with bubbles under it

[angiegirl]

I am really new to the forum & new to raising Chickens.. Our Chicks are about 12 weeks old. We have 14 (13 females & 1 Rooster) .. One of them I noticed tonight has one eye completely shut & like a bubble under it... I have no idea if I need to do something or if it is something that will pass.. I don't want to loose her, she is the friendliest with my kids. She will jump on their back when they kneel down and take treats out to them daily.. Any suggestions??