Roo or hen?

[Unearthed wonder]

Can anyone help with the sex of these 6 week old mixed batch of chicks? The white and black one I am pretty sure is a boy as it developed its comb very early and also very rose coloured weeks ago. The other is much smaller and developing a lot slower with a much paler comb. The comb is however, larger than I would have expected for this breed. (I am assuming it is some sort of a Mille de fleur)
These 2 were given to a broody silkie in a mixed flock that lost her 2 best friends last year. We will need to think about how to best integrate her back if they are both boys. (We can return them)
Thank you in advance for any help
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[sourland]

The more white bird is a cockerel picture of the other is not showing.