two african dwarf frogs should be in a minimum of a 5 gallon tank.

your frogs are not dying of old age, they live to about 5 years, sometimes up to 8-10. You frog passed away from poor living conditions.

It is not the supplier who gave them poor care - you stated you had them for a year. Any ill effects from the pet store/brookstone would have long since showed.

A one gallon tank, with few and far between water changes means extremely dirty water which is poisonous to your frogs.