I am new to the chicken business. I have 13 hens ranging in age 1-4(maybe)? Some days I get 0, some days 1, some days 2. Once a week, or so, one of the eggs is dented and very fragile They are free range hens + fed Purina Layer pellets with calcium. Some of the shells are very hard, except an occasionally very soft. AS in it breaks if I hold too hard. Any ideas?