When do you start offering scratch grains?

If a seperate chick grower is available in your area you could switch to that now.
I didn't start scratch grains until my chickens were about 6 months old, which coincided with the weather turning cooler.

 

In my local feed store they sold three types of food:

-chick starter
-pullet pellet
-layer pellet

so we could change their feed as they grew older. You could also try cleaned wheat- we fed ours lots of clean wheat along with their pellets. They seem to like it better than the food.

 

8 week old chickens still need the protein content in "grower". Check your local feed store. They should have the starter/grower, grower/finisher, and laying pellets. There should be directions on the back of the feed to tell you when to change to each. If you do put out some kind of grain, make sure you also put some chick grit out. You only need the grit if you give them something other than the chick food. It has everything they need.