... realized they were just EATING it. I thought, ok maybe there's little things in there that they like and once that's gone it'll just be plain dirt and they can use it for a dust bath. I came back about an hour later and 75% of it was gone. I looked around the bowl, moving their shavings aside, and there wasn't a lot kicked out, so they must have actually ingested the lion's share of it... Do they have some sort of nutritional deficiency...
Yes they have a very serious nutritional deficiency its called called Lack-o-Grit. Chick sized grit (i/16 inch) should be the very first thing that new chicks are fed BEFORE any chicken food what so ever goes into their craws (crops) or into their gizzards.