I'll admit that we don't change the water as often as we should, but it's difficult because it is a 2 man job and I live with my grandfather who has physical disabilities. We tend to change more water less often rather than less water more often. However, I've tested the water regularly and its all good. No nitrate or nitrites, I don't think there's any ammonia, the pH is slightly high, but nothing to be concerned about that's just because we live in a hard water area. The temperature is generally kept between 15 and 20 degrees C.
This is the only other recent picture I have but it's much less clear than the first one. The leucistic axie is on the skinny side, but she has always been this way and doesn't eat as much as the albino, though I always put plenty of food in for the both of them.
As for feeding them just on bloodworms, I know it's not the best diet, but my friend owns my old axolotls and they have been on bloodworms their entire life and while I understand they're bigger because they're older, they also seem to have grown at a normal rate.
The axolotls were definitely less than an inch when I first got them, though I think they had only just got their legs. I got them from a pet shop that was keeping around 30 of them in a shallow 1 foot square tank, so maybe that impacted their growth?
Also I apologise for the terrible pictures