Okay...it about 6.6gal-glass cover with about 40-50 week old fry, 82F temp, 8in water with 1L/0.3gal water change per day with increase of water level from 5in to now 8in-adding more like temp dechlorinated water than being removed (good) and you are having some fry issues-some look thin-some look fat with some buoyancy and/or swimming issues-all somewhat lethargic....
I should have asked this-but....any live plants, if so, how many what species...a pic of the fry tank would help, is this your first spawn or fry rearing attempt.....bare bottom or if substrate what kind, any common snails or other livestock in the fry tank like shrimp-is the male removed, how long after hatch did they start to free swim-when did you first add food....
While its not uncommon to have some deaths and/or sickly looking fry especially for the first two weeks-you should have some healthy thriving fry if the system is healthy to start......
IMO/E-the skinny lethargic fry should be culled, increase water changes to 1gal removed with 1.5gal added using like temp dechlorinated water by drip/gravity over 20-30min
Once the tank is full-start making 50% daily water changes-with gravity refill over 20-30min
The glass cover should have water condensation on it-if not-use plastic veggie wrap over the top-it is important for the air above the water to be warm and humid for the labyrinth organ and that is gong to be developing soon-usually starting in the 2 weeks range up to 5 weeks
I have never fed banana worms and don't know that much about them as far as size, nutrition.....
But with microworms-offer small amounts 3 times a day and observe them eating-watch their tummies for fullness-they should look round
If you have live plants add more to the water column to give them a place to rest near the top and if you have any common snails add a few to help create infusoria for the small fry to feed on, to help clean up uneaten food to prevent decay and fouling the water and to eat any dead fry before they can decay.
Stay on a 12h photoperiod-light on for 12h and off for 12h....
Good luck....