Congrats on your chicks!
If they are over 2 weeks old and not that frail, I think it would be best to clean them before they have too much on their toes.
You can do so with some warm water and a q-tip or toilet paper and gently wash it off and dry their little feet before putting them back in the nest. You can also wipe the poop off the nest with a paper towel while the chicks are outside so they can return to the nest with their feet and nest all cleaned.
RIP sweet Tito (Summer 2008 - January 17th 2013).
You are missed and never will be forgotten.
Yes definitely wash it off, otherwise it can and does cause all sorts of problems. It dries hard like cement. Gently wash with warm water, how about some pictures for us please?
Thanks very much for your reply! I've got some pictures below of them, three have come out of the box so far, and I realized today I actually have 2 more in the nest box who are due to come out soon! Here are some pictures of them so far including the parents!