sick new baby chick

[Lovemyfarm]

Can someone help me please. I am new at this, actually came home from camping and there was a baby chick in the coop. Now there are three. Well the newest one seemed yesterday to be sluggish. now this am it is acting like it has trouble breathing and it looks like phlem is coming out it's beek? What should I do? Thanks for your help. I did put it in a box and put a little straw in it a dish with water and brought it in the shed. Thanks.