I have 2 hens that are brooding eggs. Sadly, for some reason, none of the eggs have hatched. Its been over 2 weeks now past hatch date and the hens are still brooding. Will they give up on their own, or should I just take away their eggs? I really wanted some chicks and I have some extra fertile eggs - could I put them under the hens or will the extra 21 days be too much for them?