I use the scratch and peck herbs with awesome success. I am on my 3rd hatch with no issues or sickness yet.. I think as long as you are conscious of the properties of the herbs you should be fine. Just don't go adding things like boneset and you should be just fine..
I like rosemary and sage, but only when cooking them.
Seriously, herbage is more for the keeper than the chickens.
The chicks just need a good balanced chick starter ration and plain fresh water.
Best to get granite grit. http://www.jupefeeds-sa.com/documents/GraniteGrit.pdf.
I bought about a 2 gallon bag of granite grit from the local mill, they put it in their chicken scratch. Ran it thru a colander with 1/16" holes. Bagged the smaller stuff for the chicks and sprinkle some over a chunk of sod in the brooder during the second week.