feeding new bantams

[Mykee]

I am buying a pair of golden Sebright banties next week. They will be just under a year old; one cockerel and one pullet. The breeder is feeding them an 18% protien layer crumble. Where I live, I cannot buy an 18% crumble. The closest is a 15% layer crumble. Will this protien change disrupt their systems? Do they need the extra protien?
I'm so excited! Can't wait for my babies!