ChickenCrossing.Org

I have 8 Buff Orpington hens; 2 girls born last year and 6 born this past spring.  The 2 older girls used to lay or at least 1 of them did. But that stopped a couple or so months ago.  Now the younger are older and the same size as the older but, none of them are laying.  I haven't had an egg in forever.  We thought it might be the heat (we live in N. Florida) but the temps have cooled now that we are into the fall. But we still aren't getting any eggs.  They are fed layer pellets and oyster shell mixed in for the calcium so they could make strong shells. There is a chicken house with hay for the nesting boxes and they have a safe confined run so dogs or other predators can't get to them.  Any suggestions as to why we aren't getting any eggs?