I know that Todley wrapped her plants' roots in mesh bags filled with flourite subtrate, then you can bury the bags under your gravel. I think that's a great idea! The flourite is nice because it's rich in iron and some other minerals that the plants like. You can put fertilizer sticks/tabs under each of the plants that are root feeders. Also, you can add fertilizers to your water. But you have to keep in mind that the nutrients and plants and algea in your tank are all doing a balancing act...too much of one thing and not enough of another and you could be an algea farmer. If you have higher lighting, your plants will be going through photosynthesis faster than if lower, and will require some additional nutrients, however, they will also require some CO2 to be able to make use of those added nutrients.

Is this the tank that is going through a cycle? If so, I wouldn't even think about fertilizers until it's done. If I were you, I'd just keep an eye on those plants for a while. Once they begin to establish themselves you will be able to tell what they might need. Ferts don't hurt fish, and my guess is that frogs are okay with them also. But, you must use aquarium fertlizers (unless you are a junior chemist and want to make your own...but I couldn't help you there at all...I'm sure Del could though;) )

Just get those plants anchored first.