Purina Flock raiser would be a better choice.. higher protein and amino acids.. equals better growth... especially for these larger dual purpose breeds.
ALL chick starter used to be 22% protein when I first started keeping chickens a little more than a decade ago.. recent years past.. they've all been reduced.. to what is essentially a bare minimum.. more profit for the feed makers.
Feathers are made from 90% protein and it's amino acids. Muscle is made by protein..
I know plenty of folks raise their chicks on that and never notice the difference.. but as an avid and passionate breeder/hatcher I've been appaled since I first saw 18% protein chick starter.. I don't wanna go off on any tangent though.. I will note energy comes from 3 sources.. carbohydrates including fiber, fat, and protein. When protein goes down carbs goes up. 22% protein was shown in studies to give the best hatch rates. I experimented all the way up to 30% protein for the breeding flock and rearing chicks.. That high reduced hatch rate, so carbs are STILL an important energy source. Excsess potein is excreted as extra (nitogen) smelly and expensive waste.
Just some food for thought.
Your babies are beautiful!