Absolutely stunning! Your tank is excellent too.
TBH, about the bettas being very hardy thing... I don't think all the inbreeding for finnage and colour is doing the bettas much good health and strength wise. I too keep up good tank husbandry yet have lost a lot of very nice fish - mosty dragon scaled and HMs that were imports.
Not all bettas are "hard as nails" anymore in my opinion, and it's a real shame!