1 guy in our club had a yearling this season win 6 1sts club 1st fed 2nd fed and lots of other top fed positions in fed that pigeon is in the bhw this week he won 3rd under 300 mile homoform challenge that pigeon was on darkness as a youngster also only had 2 yb races and stopped cuz of yb sickness so that tells me that neither yb sickness nor darkness has any affect on the pigeons as yearlings but you can make up your own minds.