A pale comb is often among the symptoms of various diseases 'n such, but not w/o additional issues ... it'd be a good idea to read over the Diagnosing Dieseases Based Upon Symptoms link below, as it often helps folks to spot things they'd previously overlooked.
Also, add Apple Cider Vinegar to their water (but not in galvanized containers) for all of your birds, at the rate of four teaspoons to the gallon (the target pH is 5~6, or slightly acidic). The tannin in ACV helps to 'cut through' the mucus and coating w/in the mouth, throat and intestines, which improves the uptake of nutrients/vitamins, and also helps them to expel the excess and toxins from their systems, and boost their immune systems. It also create an environment hostile for internal parasites, and is used to treat exposures to the toxins botulism forms, and algae poisoning.
For certain, this will do no harm to your birds, under any circumstances I've ever encountered ...
Although I've documented my every claim for the above benefits, I've none to offer for my personal manner of phasing it in and out in a cycle of every three days or so, by increasing and decreasing the concentration. But, initially, you could add two teaspoons to the gallon, followed by three teaspoons to the gallon, and then four ... you get the idea. Most folks just give it continuously, but my theory is that my method allows the birds to more naturally adjust to their environments, and all the benefits I'm lookin' for are accomplished w/in those three days (which are repeated often enough to continue the benefit ~'-)
