One of my girl's comb has gone from red to light pink this week. Upon further examination this morning, two of the other girls (also 19 weeks old) have a very small black spot on their comb. The girls all free range on my 1/2 acre. They are still on the chick starter since they are not laying yet. (It's Purina food; bag says it is medicated.) Should I be concerned about the comb changes?