+sad story+ but want answers on what could do this??

I had given two juvenile axolotls to people who had set up their tank properly and let it cycle for about 2 weeks before. They picked it up at 4pm, by the time I as done by 8pm they told me they thought they were dead. I went over to see and one was floating with burnt looking gills and had slime coming off of him like oozing, the other was at he bottom, all its pink limbs had turned cherry red and it's gills had looked burnt off . I quickly scooped out the oozing one with my hands and he felt like dry rubber. He had passed. Within the seconds I picked up the second he was dead too.

I was shaken, I as so upset, these poor babies I had raised for 5 months. I got home and researched to see what could have caused this? It was so extreme!

What had happened here? I have many people who had gotten axolotls from me that have city water and this had never happened. This was the first time I went someone have a canister filter though. They told me they were going to take their water sample into petsmart to get it checked. They felt horrible obviously that they didn't do a water test before.

The tank probably wasn't cycled because it takes 6-8 weeks to cycle a tank, and it was probably during the ammonia spike of the cycle, and probably ended up with chemical burn. I am so sorry for your loss, it is really hard loosing an Axie, My first Axie ended the same way, because of a filter problem I didn't catch.