I think I know the difference. Demi's a wild-type mixed female, but ehr tummy's definitely bigger than the boys at any time. Seiya and Kalec don't get big tummies at all, but Phy did occassionally.
Do you think a bigger, more solid body is a healthier betta? Or maybe just a stronger one?
I sometimes get worried looking at Seiya (cause he's light colors and the effect is more severe) but he looks so thin even though I know he eats his two meals a day (omega one pellets with a few meals subbed for frozen blood worms).
Kalec and Seiya could also be young I think, but it's hard to tell when the LFS sells you the fish and they themselves don't really know. They're body-length's are about 1.5 inches, so obviously safe to travel, but beyond 3 months how do you tell a bettas age, right? For a while I figured going by the pelvic fins on males was a safe bet, but nothing's really accurate unless you have it from a baby or know the breeder. Kind of frustrating.
Another thing that makes me think Seiya and Kalec are young is their finnage. I bought Seiya labelled as a halfmoon, but he never flared far enough so I figured he was mis-labelled and was actually a Super Delta. But then I got a great shot of him flaring a full 180, so now I'm wondering if he's simply young and his fins are still filling in. Same with Kalec, I think he has nice finnage, but it doesnt look...complete? Not sure about all CT's, but his fins/rays end rounded.