i would move them to a larger tank now, as keeping them in a small tank will cause aggression and stress, which could ultimately make the fish ill or worse. i personally would set up a 20 gallon long with two sponge filters on a gentle flow for these lil big bettas.
the tank they are currently in is the perfect size for spawning a single pair, but for growing out the babies i would have something bigger, say a 10 gallon minimum, to keep the dilution of wastes between water changes at acceptable levels. as you probably know, baby fish need to be fed more often than adults, and that creates more waste in a tank.
that is a very nice little tank, i'm sure they appreciate the tannins coming from the bogwood, and tannins, blackwater, etc do help to induce breeding in bettas.
a tip on taking photos, do it with the tank light on, you'll get much better pics!
good luck with your breeding! your lil big fish are very cute!