Question: Axolotl Size vs Age

I have searched all over the forums here, and on Google, but I haven't really found a solid answer.

I have had my axolotl, for 4 and a half months now. I keep Guadalupe in a 20 gallon long tank, with a proper filter, proper water levels, ph, nitrates, and no small rocks just a bare bottom so cleaning and feeding is easy. I feed him earthworms/nightcrawler chunks, or guppies (whatever is in season here in Canada)

The thing I am a bit worried about is his size. He has barely grown at all! Only his tail has doubled in size and he has grown a tiny bit in length. His belly has fattened up a small bit, but he is only 10cm long, and his belly is not quite as wide as his head.
I'm worried he is either from a strange batch of really tiny axolotls, or he may be sick.
His gills are pretty small, but quite fluffy. His tail is straight, he doesn't have any strange patches on him, and his gills stand up backwards and look relaxed.

Should I stop worrying?

He's still a baby :happy: Axolotls come in all shapes and sizes and grow at all different rates! I have 4 axolotls all the same age (approx 9 months) ones 8 inches in length and then another's only 6 inches! They're all fed the exact same diet yet still grow at different rates. My eldest is a 5 year old girl at a titchy 7 inches whereas my biggest is a whopping 10 inches and is 2 years old! Alas it is true, you do get dwarf axolotls but at this age I don't think it's anything to worry about. You've got him on a good diet, he's just got to have his growth spurt!