Lavender Sussex - boy
BLR Wyandotte - boy
Barnevelder - girl
?Red Sussex - girl
Just my guesses, I'm am fairly sure that the Wyandotte is a male due to the super pink comb at this young age.
This only works with a chick that has one parent from a fast feathering line and a parent from a slow feathering line.
Vent sexing is the only 90% guaranteed way.
As for the genders, I think the Lavender Sussex is your only cockeral, all others look female.
Your "platinum" Sussex is either a silver, white, or lavender. Platinum is not a recognized color. Also it's comb doesn't look to be a single comb.
I agree that the last one in the pictures is a Buff, your bird is way too light colored with no specks.
It is too early to tell gender yet. Give...