It's not frost bite and you don't need vaseline. Just make sure your coop is DRY.. with no moisture running down walls or windows and no condensation.. Ventilation (of exhaled moisture) is KEY to preventing frostbite. Closed up tight can be more harmful than not depending on things like stock density, enclosure size, etc.
Frost bite would start at the tips not on the sides. Pea combs are generally not that susceptible to frost bite the way straight combs can be. Most birds will tuck their heads in under wings or feathers to keep face warm. If frost bite does happen to comb
tips.. they most often fall off and heal up quickly to not be frosted again in the future.
How cold are your nights? Are the Silkies roosting yet or piling still? Are they off daytime heat or been "hardened off" in any way, and were they raised with or without a mum? I see snow.. but as long as it isn't windy and they aren't soaked to the bone.. Silkies are fairly hardy little fluff ball buggers!
Redness is hormone related and can vary throughout the day and by season or age sometimes and yes when feeling under the weather too. I agree I only see.. peck or scratch marks.. maybe dry skin.. but NOTHING of concern!
Good eye paying attention though!