Is this a birth defect or stress?? New mommy worries

Hey there!
I'm a relatively new axolotl mom, so I have been kinda stressing myself out that my axie is stressed :dizzy:

I was worried about Axel Rose's tail since it started getting more flecks of white in it, but I learned from the posts I've been scanning that this is probably just him growing up and getting more of his normal coloring, I believe hes a golden from pictures I've seen.
My question now that I've been looking at his tail, is I noticed this curled little bit at the top of his tail ever since I got him. Is this what people mean when they say their tails curl from stress?? Or is this just a birth defect? Pictures are below (sorry they're sideways, cant make them go straight for whatever reason)

Side note: Deep Breaths, I know, but between worrying constantly about his tank temp (I live in southern US, its 90°F on a "cool" summer day, and of course his tank temp decided to spike to 70 the day after I got him in there, after having constant 65 for the 3 weeks I was letting it cycle. Finally fixed now with fans and frozen water bottles to 63.) and parameters (everything says nml on my testing kit) and making sure current wasn't too strong since hes alot younger/smaller than I had planned to be getting! No to mention he seemed to throw sand up constantly, making it always cloudy so I had to switch to large glass pebbles. Ugh, Does it ever get less stressful? LOL At least hes a really good eater on red wigglers cut up (I hand feed him with a pair of blunt edge tweezers since my kids love to watch him eat and he is really bad about not finding food unless its right on his mouth. He is pretty crazy when he eats food, but its kinda adorable to see this 2.5 inch little thing guy be all aggressive)

(S)He looks absolutely fine! Maybe a closer picture of the tail I could see more of the curve you are talking about, the flecks in his/her tail, I would say would be more of his/her colouration coming in! Gorgeous baby!
As long as the temperatures dont stay over 65 degrees for too long (s)he will be fine, and make sure temperatures dont fluctuate too much, any large temperature change in less than 30 minutes will stress it out, especially if it changes too often. Its okay if it kicks around the sand, it will settle after some time, but since (s)he is adjusting to its new home (s)he will be a little skittish.
I would look into investing in a Chiller with how hot the temperature is where you live, but for now if you keep the temperature between 60-63 degrees it should be fine!
Overall absolutely gorgeous!
Any other questions, I'd be happy to answer!

Honestly they look fine and it looks to be iridophores. This is normal on especially golden and albinos. The curly tail is only really a problem when paired with gill curl but do a water change to ease your stresd but it should be fine. Keeping you tank between 64-68 is optimal but can withstand temps up to 74. It's that you won't see much growth but your axie won't be stressed. Anything below 64 can lead them to be sluggish and won't eat much but won't stress them out similar to higher temps. You really don't need to change the substrate because spitting sand is normal behavior with axolotls (unless they are digesting it then throwing it up with food then see a vet asap). Good luck on being an axie owner! :happy: