I have six seven-day-old chicks. They are different breeds; two of them are leghorns. These two have developed a strange lump on one side of their chest. They seem healthy, so I wanted to know if this is something I should worry about or if it just a normal developement on this breed. Called my sister, who got her chicks from the same place, and she says her only leghorn also has the same lump. What is this thing? And is it contagious?