I have 3 RIRs, 3 Black Australorps, 2 Buff Orps & 2 "Americaunas", all 21 week old hens. Only 1 of the RIRs is laying (little bitty eggs). Since they were about 3 weeks old, they've been fed non-GMO, non-soy feed. Am I missing something I should be doing to encourage laying with this kind of diet or is it possibly the cold weather?