So, your birds could be closing in on two years old? It may be that their age is showing. Believe that some breeds are only really productive for two years. Does any one here in the forums have experience with OP's breeds, as far as the years egg production?
Would suggest supplementing...
We need to know two things
1) Were they full size when you got them, were they small when you got them, or were they big but still growing?
2) How long have you had them? Did you get them three months ago or three years ago?
Riki