My ducklings are 10 days old. I got some small sized chick grit and I just noticed it says to start offering it at 2 weeks old. I gave them shredded lettuce today for treats so they need grit. Can I use this stuff even though it says to wait until they are two weeks old? Is there something else specific to ducks I should be using? In the meantime I gave them some sand from our creek but it's super fine.