Tails wounded or infected?

[rjasi]

Hi! Would really appreciate anyone's help. I'm a beginner axolotl caretaker. I have 3 axies in a 50 gallon tank, no bottom substrate but with driftwood and some dragon stones. I keep them more or less at 20 celsius temp and I have cycled the tank (water is always clear, I only change every 2-3 weeks). I feed them carnivore sticks and pellets. Yesterday, I noticed their tails look "cut" or wounded which has never happened for the past 6 months that I had them. Is this because of an infection? A harsh environment? Are they attacking each other? Please help. I have attached some pics

 

[wolfen]

looks like tail biting to me as the tail is suddenly missing rather then a gradual reduction that fungus would cause, you might have to increase the food to prevent fighting, also keep an eye on their tails as they are wounds. the first photo is a newer injury than the second as the tail end on the second is already regrowing and rounding off.

 

[Autistic Catholic]

If it's not infighting, it may be the environment. The stones look rough, so is driftwood. Axolotl skin is cartilage and is very delicate. Imagine rubbing your earlobe on a dragon stone or driftwood because your earlobe is also cartilage. Try smoother surfaces in the tank.