Six weeks is far too young to try to sex. I've seen combs like that become pullets, and I've seen that suspicious crest become a poof.
At this age, you're missing a few signs that will come along in the weeks ahead. Usually, for me, it's around 4 months when we can be pretty sure. Buffs and chocolates can take even longer. I have a growout pen with 8 silkies, about 4 months old, and out of them, I'm only sure that one buff is a cockerel. The rest all look like pullets, but that's against the odds.
More signs I watch for is their crests, hackles (cockerels get long narrow feathers coming from their head down the back of their neck) and their tails. Pullets usually have neat, round tail feathers, cockerel's tails are messy-looking. But they won't start getting these things for at least a few more weeks.