I agree with @Rhodebar Lover looks to be a pullet right now for the Brahma, there's a bit of growth at the top portion so I'd still keep an eye on it.
I understand the frustration with all the cockerels though, my first round of incubating this year was a 100% hatch. I only managed to hatch 2...
Yes it's part of thier circulatory system, so if they're overheated they flush just like our faces do. Is your Brahma getting a lumpy looking comb or just seems more prominent than before?
Okay well we can do reverse, lol. This is a Dark Brahma pullet at 16 weeks to compare combs. It showed some color starting about 11 weeks, more red looking when they are hot