Jo-Anna, thank you for the recommendation. These are my very favorite animals, and I am so glad to hear there is someone out there who is taking an interest in them!

Your tank set up looks nice, I would just make sure all of the edges on that hide are smooth. I would also give each of them their own hide, as they can be territorial. The absolute best food for them is a nice, juicy earthworm. Make sure it comes from a pesticide free environment, and you can just feed it to them by hand. With your new filter, make sure it does not create a lot of current, as they don't like it, and a 30 long tank would probably be best. I do believe the gills should grow back, but it is really Axolotl dependant. I can't tell from the pictures if you have males or females or one of each, and you really can't tell until they are older. Again, I don't know how old yours are, but if they are smaller, there is no point in looking.
I sure hope I helped, and please do not hesitate to contact me if you ever have any Axolotl questions. That goes for everyone!
Also, feel free to root through my photos for setup ideas, I think I have some full tank pictures, and if not, I'll put some up.
Good luck with your new friends!
Hannah