Researchers often study high numbers of animals in very limited spaces. Just because they kept 2 axolotls in a 10 gallon tank doesn't mean that's the most comfortable option. I personally have one axolotl in a 10 gallon tank right now due to a tank size limitation at my residence (a school--I have a 20 for him at home) and the 10 gallon is honestly too small for one adult. You mentioned that yours were juvenile, but they look fairly large. The only time I would say a 10 gallon is big enough for 2 is if they are both under 4 inches long. Otherwise, there's just not enough space for them to move around comfortably and they'll end up in each other's spaces all the time, which could easily lead to injuries. Please get a larger tank for their sake. As someone else suggested, you should probably have at least 30 gallons for two axolotls.