Hi Thya,
What lovely photos you have there. I see you have for them a lovely home with hiding places and plants. And both of them look well-fed!
However, sometimes when the axolotl's gills are curled forwards, it could mean they are stressed. Im sure you are a good axolotl guardian and want your babies to feel all comfy. I would suggest you might like to see if there are strong water currents in the tank. If you have a filter, check that its not creating strong swirling currents, it may be making your axolotls stressed. Also check that the water temperature is not too high. An ideal temperature would be around 17-18 degrees celsius. It should not go beyond 24 degrees celsius for a duration of time as axolotls can feel stressed from high water temperature and get sick more easily.
Also its generally better to use clean fine sand on the bottom of the tank rather than gravel. This is because axolotls feed by almost a 'vacuum-like" action with a big gulp and may ingest in the gravel in the process. The gravel can cause impaction (being stuck in the gut) and can make your axolotls sick or even die.
Feel free to ask around if you have any questions. There are plenty of experts on this site who can definitely assist you.
Best regards