Defiantly do not feel bad about not controlling the fleas! It sounds like you are doing all the right things. I would keep up the treatments and hopefully you will be able to get ahead of them as winter sets in. I know that you don't get super cold in South Texas, but hopefully it will be...
According to this, you will need to treat the ground as well as your chickens.
https://www.merckvetmanual.com/poultry/ectoparasites/fleas-of-poultry
Edit, missed where you said you have already been treating the ground....