https://www.backyardchickens.com/threads/removing-poop-off-quail-feet.759923/
I was thinking about suggesting keeping a small tray of wet sand but I do not know that would work, then I read this thread and something similar was suggested.
I wish I knew how to help you. My husband used to raise quail and he kept them on sand. with some leafy branches piled up at one end of the cage. They were older than your babies.