4 from Ideal - Forgot who was who!!

So I got 4 chicks from Callahans (they get them from Ideal Poultry) and of course forgot which was which. I got a barnevelder, silver gray dorking, cuckoo marans, and an australorp. I just had to get them because I've been wanting to try all these breeds. Can anyone help identify who is who?

Chick One: brown with strong markings, very fluffy

Chick Two: Lighter markings, 5 toes (I think this is the dorking)

Chick Three: Black with yellow/white, less fluffy


Chick Four: Black with fluffier head and markings on face



Also, I read somewhere you can put sand in the brooder for grit and baths. They are going to town with it. This isn't dangerous, right?

Thanks for your help!