Bettas need a bigger setup. The reason being is they require a heater to keep them at a stable temperature of 78F -84F. If you can not keep the temperature stable and warm, they will be stressed and are more likely to get sick. I do not recommend anything under 2.5 gallons and that is pushing it. With the space you are taking up with all the 1 gallon bowls and 1/2 gallon containers, You could easily get a couple of 5 gallon tanks and divide them each to hold 2 bettas or a couple 10 gallons(which might actually be cheaper) and divide them to hold 4 bettas which would be much better for your bettas. Bettas are better off in larger containers and enjoy lots of space. The thought that they like smaller environments comes from the wrong assumption that they come from muddy puddles in the wild. They originate in rice paddys which span miles upon miles of shallow very warm water. Most bettas do not like a lot of current but there are ways to make the filters not produce that much current to help them out. How often are you changing the water in your "tanks"? For the ones under 1 gallon, it needs to be 100% every day and on the 1 gallon ones 100% every other day to keep the ammonia from hurting your fish. I know you love your fish which is why I am giving you some advice on ways to help them as much as possible with as little extra cost as possible.
