They sound stressed. Chickens like routine. Check the loner out as previously mentioned to see if she is sick or injured. Then get them in a coop at night with nesting boxes. After only a few nights of being shown where to sleep they will put themselves to bed around sundown. An added benefit will be you only have one place to look for eggs. Leaving the birds loose at night leaves them vulnerable to other critters. Just my two cents. Good luck. PS - if the duck is picking on them, keep them separated.