Bad weather can implicate they were inside a lot and a 8x8’ coop gets easily overcrowded with such a variety of breeds. . Stress can be a factor.We love in Salinas calif. There run space is 16' x 23' and the co-op size is 8'x8' with 16 next boxes. We feed them lay crumble , scratch, they get oyster, grit,and meal works very other day. No they do not free range.. No new birds introduced. We have had a lot of rain lately
Did you check on red mite? Its time to check every week as soon as the feezing stops. Red mite weakens chickens. They stop laying and are a danger for their health.