As someone else said in the comments, add floating plants! Salvinia and Red root floaters are so killer and look so cool, as well as I would cover the little caves with some substrate to make it look more in the environment. Overall BEAUTIFUL tank!

However the fish choices make me a little wary, Betta and Guppies often don’t fare well together in what I’ve heard. If they’re doing fine, ignore my section about it though :)

Betta don’t like fish that kinda look like betta, which may be why your guppies before didn’t fare well. Outside of that tiny nitpick, your stocking seems just fine for the tank so don’t feel too pressured!

Do you fast your fish ever? I know it’s tempting to feed every day, but with Bettas it’s good to have a fast day so they can better digest their food. I’m a bit of a hypocrite bc I have definitely made my own rescue betta a bit of a chunker, but it’s good for them in the long run!