2 more weeks until my chicks arrived, so I am going to buy and prep everything for them this weekend. I will be getting 4 chicks. It seems the starter feed they have at the stores is 18% protein which they'll be on until 16 to 18 weeks of age. Approximately how many pounds of food do you think I will need for 4 chicks for that time? It seems my options are 25 or 50lbs bags.