There could be a couple of things a play here.
Let’s look at your flock nutrition. To make sure your layers are provided with adequate nutrition, they should be fed a balanced and complete layer feed free-choice, and the treats you feed should make up no more than 10% of their total diet. Given the severity of your situation, I would even cut the treats back further. Too many treats throw the nutrient balance off and can hinder performance. Adequate amino acid availability, calcium and phosphorus are of particular importance with older hens.
Molt is an unlikely culprit, as even the longest molts are only 6 months long. But, your hens could be facing other stressors, such as space, nesting area comfort and access to enough light. They are also getting considerable age on them and may simply have reached the non-productive stage of life. You may want to have them checked for parasites, which can rob them of the nutrients in the feed. Predators lurking around at night could also be a stressor. Even something innocuous to us, such as construction noise, could be a potential stressor.
Chickens need adequate space to be comfortable, so make sure your hens are offered at least 4 sq.ft/bird inside and at least 10 sq.ft./bird outdoors. From your question, I am guessing you have around 10 birds, so your coop should be at least 40 square feet and their outdoor space should be 100 square feet.
Check the nesting boxes. Make sure that there is plenty of soft, clean bedding material in each nesting box. Hens prefer to not lay in dirty or unkempt nesting areas.
Your hens will also need a proper light:dark schedule – 16 hours light, 8 hours dark per day for optimal egg production.
Hope this helps!
