What breed is this guy?

[Theleghornchick]

I bought this guy about 8 months ago from ideal poultry as a mystery rooster and still can't figure out what breed he is, he has been growing very slowly compared to the other chickens I bought around that time so I was wondering if he might be a larger breed?

 

[The Moonshiner]

Delaware

 

[Theleghornchick]

Thank you!