Hyperlotl?

So i have been thinking about my 2 axies and i have realized something
Burrito is very relaxed and likes to crawl through the water and will come to the tank's edge to see me when i enter the room
she tolerates me sticking my hand in the water and will let people gently hold her at the water's surface
she's somewhat playful and chases my fingers from the other side of the tank
meanwhile, tortilla (who is still in a different tank) is a total nut
she's so shy and will dart about even if im just trying to feed her
i know with my toads the males are much more timid and crazy than the females but both axies are female
could it be that tortilla is only about 16 months old? or that she is wildtype and thus has better eyesight so is more easily startled? do they just have different personalities?
anyone else notice differences in their axolotls' behavior?

All 4 of my adults are pretty calm.

Tortilla might just be hyper, or maybe there is something different enough about the tanks set up that she feels less safe. Is the lighting or anything different. Different types of hiding places? Perhaps more exposure to your presence would help her realize that you are the bringer of food and nothing to fear? Or like you surmise, it might just be her personality.