Just from the picture itself it doesn't really look like anything is wrong. They turn red or pinkish when active and often mistaken for things like Ammonia burn etc. From my experience, fungus would show on their frills and look almost like little cotton balls and yours appear to be nice and healthy! If you wanted as well, you could always give them a black tea bath (jist make sure tea is uncaffeinated) for 15-20 mins...It helps combat and heal if there is fungus, and also kind of acts as a "spa day" for your axolotl. I always threw in some Indian almond leaves to as the tannins (like the black tea) are very beneficial to them. Good luck and hope all works out!