Illness/Sickness: Vein or growth on tail fin?

I have had my water children, Briar and Lancelotl, for about 5 years now. They live in a 20 gal tank, fully cycled, live plants (a few pond snails here and there) and a single white cloud minnow who survived being eaten for 3 years. Their water parameters are ok (not perfect 0s across the board, but no ammonia). A tornado touched down and wrecked quite a bit of the city, stressing my axolotls out via vibrations and power outages that knocked my chiller offline. I generally keep the tank at 58°F, though it got up to 64 before the power came back on.
I noticed this odd, vein-like growth coming out of Lancelotls tail. Lance is leucistic so this odd red growth really stands out. This was not here a few days ago. Is this damage from thrashing about being scared?
I have attempted to attach an image, I hope it works! This is my first post.

Hard to see whats in the pic , from your description it just sounds like the axolotl bashed itself , its equivalent to a bruise. If youve got the water quality and temp back to normal it should be fine.