Its always OK to swap over to All Flock, assuming you have free choice oyster shell available for those still laying. We get dark about the same time here, and my egg production has dropped substantially, but not stopped.
Many recommend mixing the two foods as you introduce, so the flock doesn't turn its beak up at the sudden change. I've not had that experience, but its such a simple thing, I see no reason not to do it. Buy the all flock when next you are out, add a little to your layer. as you finish out your layer bag, keep adding more all flock till they've completely transitioned.
I will say that All Flock is slightly more expensive, if that's a serious consideration for you - circumstances differ - but the higher protein content is of benefit in adding weight to your meat birds (which you don't have), the lower calcium is better for your roosters (which you don't have), hatchlings (again, you don't have), and is generally believed to make for faster, less stressful molts when your layers start replacing their coats.
. I give a handful of mealworms instead.
