Welcome to the forum.
Frogs in most cases are not to be combined due to the chance of one poisoning the other. Each species secretes different toxins and frogs absorb drink, chemicals, and so on through their skin. When they travel the same areas, use the same water, they slowly poison each other.
In the wild, they are not confined and rain, wind, continued changes in weather cleanses things so you will find multiple species in one area, but in the confines of a small space it is a slow process of decreasing health.
It is recommended that your tanks be 10 gallons per frog and the more space provided the better. When setting up a tank, one should keep in mind the conditions the frog comes from. IE: tree frogs should be provided height, vines, branches, and so on since they are not found on the ground. Where as a toad will did up substrate, climb on low lying objects and crawl up under vegetation.
Hope this helps.