You can’t do anything to make a hen lay eggs, but you can make sure she has everything she needs. A plain seed diet is not adequate nutrition, especially for breeding birds. They need a nutritionally balanced diet like pellets or our foraging diet. Our foraging diets are nutritionally balanced the same as a pellet but they are not ground up. They do contain fresh, whole seeds along with other nutrients they need. Loose seed mixes are generally not fresh and offer very little nutritional value. You should also offer chopped fruits and veggies, multi grain bread and cooked eggs. I would first improve their nutrition and then see of they have more success breeding.
Breeding birds also need privacy, so only check on them when you need to give them food and water. If you check on them a lot, it can make the nervous and not want to lay eggs.
Here is a feeding guide to help you:
Bird Food Guide
Thank you for asking Lafeber,