I started them on some probiotics and electrolytes to assure coccidiosis is not a factor and noticed too that one of them will sneeze every now and again. I'll take a pic of both when I can and see if I can get a pic of Brahma laying down with the discoloration.
BTW.....Probiotics and electrolytes will do nothing for coccidia.
15% is a bare minimum protein level, IMO, I would not be feeding any other foods that would dilute the protein level further.
One week is not long to adjust to a new environment, give her some time.
ETA: azygous gave good info on the changing comb color.
This drove me nuts when my pullets were close to lay and I was observing their combs closely looking for them to plump and turn redder....they would look very red, then pale out again as I was watching.
I like to feed a 'flock raiser' 20% protein crumble to all ages and genders, as non-layers(chicks, males and all molting birds) do not need the extra calcium that is in layer feed and chicks and molters can use the extra protein. Makes life much simpler to store and distribute one type of chow that everyone can eat.
Calcium should be available at all times for the layers, I use oyster shell mixed with rinsed, dried, crushed chicken egg shells in a separate container.
Animal protein (mealworms, a little cheese - beware the salt content, meat scraps) is provided during molting and if I see any feather eating.
The higher protein crumble also offsets the 8% protein scratch grains and other kitchen/garden scraps I like to offer.