Betta scales health question

Hello!
I have been a Betta parent for about a month so if Salvador does anything different or looks different I immediately research, but I'm overwhelmed with info.
Question referring to the below and the pictures I've attached:
He has sort of silver/white coloring at the base of his (tail?) and it seems like discoloration on the base if his fins where the scale coloring. The pattern is uniform and ich isn't, but I want to get some guidance: does he have ich? Some other illness or problem? Do his fins look ok or is he beginning fin rot?
Apologies for the amateur novice questions, but I love him so much and I'm so new that I don't want to assume he's fine.
His water gets changed 1/4 to 1/3 every week, his pH and other levels are perfect according to the API Master test, there's no food waste because he eats everything I give him.

 

Definitely doesn't look like ick, too big and non-random. Fins look pretty good to me. Finrot typically starts on the ends, anyhow. My guess is some sort of color change going on, which is pretty common in bettas.

If illness, would think fungus. Just can't really tell.

More importantly, has behavior changed?

 

Hi!
Thank you so much for responding, and your patience with my probably over protective questions. I feel better about his color.
Not too much change. He had been resting a little more in new places (substrate, the back of the aquarium by his heater (not when it's heating), his cove instead of his hammocks), but as soon as he saw me he came swimming up to the front of his aquarium. And he built a bubble nest.
Today he's behaving his normal active adorable self.
Just in case the places he was resting means he's bored I got him some more interactive toys.
Last newby question for this concern - would a fungus be uniform like that? Or the color in his base of his fins? If so which and would it require aquarium salt or a specific treatment?
Thank you all for helping me keep little Salvador healthy. He's a rescue and I have no idea of his age but I know he wasn't cared for properly until I got him.

 

So, from my experience, that can be a coloring bettas have, some of mine have had it before. I'mnot seeing anything that looks like fungus, so it's probably just coloration.

 

Thank you! I'm really grateful for how supportive and rad people are here.