@infinita est lux Solis  
Not necessarily the pink marks, since Philomena doesn’t have them (or at least she only has a tiny bit on her beak), but the head crests do seem like a consistent form of sexual dimorphism. Both Philomena and Peewee’s mother have the crown-like structure, while Peewee and his dad have the more “conventional” crests.
 
Actually, another thing I notice is that phoenixes seem to have quite a bit of variation in terms of color. Peewee’s mom has her pink markings, his dad has the yellow flame-shaped marks on his chest, Philomena has a comparatively basic red and orange color scheme
 

 
And Peewee has a lot more yellow and light orange than other phoenixes.
 

That’s interesting, male phoenixes have feathers on their head and yellow marks on their breast, while females have those antennas and pink marks.

Hope PW’s parents had forgotten about the rock incident