I have 12 week old chicks still eating chick starter crumbles. However they also eat all manner of treats (kale and green apple are their favorite non-worm and grub food!) and scratch. They peck and scratch and eat off the ground in the run, so I know they're getting dirt particles and (I'm assuming) tiny rocks and such. Should I put out some grit also? At the store today I bought a small box of regular pet bird grit as they didn't have anything for chickens. Thank you!