You are correct in identifying the comb types. It is rare to have a Wyandotte with a single comb but it can happen, especially if the genetics are not great(mixed breed). Are all those birds the same age though? Because that is a fair amount of development and red in those combs for 7 1/2 weeks…I would watch closely for other male traits, although wyandottes can sometimes be trickier to distinguish. (When I had a couple I was sure that one was a boy practically until she suddenly laid an egg due to the huge difference in comb sizes

)