Sounds like you free range your birds so potentially they could be hiding eggs somewhere.
How sure are you about their ages? Assuming you are in northern hemisphere, days are growing shorter, and if these birds are over a year old they will likely molt and slow or stop laying until days start growing longer again.
This isn't correct. Unmedicated starter feed should be fine for hens and roosters and may be preferred to other feed due to higher protein content. The ONLY thing layer provides is higher calcium, which can be harmful over time to males/non laying females - layer does NOT magically make chickens lay and many folks on here never use it at all.