My initial advice is to remove the food tablet, and do another 100% water change.
I tried the feeder tablet, and it fouled the water in the tank. My betta became very ill from it. After I did a 100% water change, it still took her a few days to perk up. Bettas can go awhile without eating. But perhaps the best solution would just be to ask your daughter every day if she has fed him that day.
So that we can get more information, could you please fill this out:
What size is your tank?
What temperature is your tank?
Does your tank have a filter?
Does your tank have an air stone or other type of aeration?
Is your tank heated?
What tank mates does your betta fish live with?
What type of food do you feed your betta fish?
How often do you feed your betta fish?
How often do you perform a water change?
What percentage of the water do you change when you perform a water change?
What type of additives do you add to the water when you perform a water change?
Have you tested your water? If so, what are the following parameters?
Symptoms and Treatment
How has your betta fish's appearance changed?
How has your betta fish's behavior changed?
When did you start noticing the symptoms?
Have you started treating your fish? If so, how?
Does your fish have any history of being ill?
How old is your fish (approximately)?