In regards to getting a chick a week apart in age ... don’t take my word for it, but I would think it’s okay if you get one. My thoughts are they are too young to get the pecking order behaviors yet. I have chicks 3-4 weeks apart and in an overcrowded space - all thanks to me impulse-buying chicks from Tractor Supply. Just plopped the young ones in and they just got incorporated into the crowd. Also, if you get one, I would think that the lone one week old would seek out the companionship of the hatchling, and vice versa? These are just my thoughts so others may have different experiences.