Re: High light plants
If you think that the light is too bright, turn it down or raise it farther above the viv. Then, over weeks and months, evaluate growth.
When the plants dies and you took them out, how did the root systems look? Typically, plants that are overlit will drop leaves (scorched, rather than yellowed), and try to regrow new ones that are acclimated to the light levels. If the roots were less than healthy looking, suspect poor drainage, poor airflow at the roots.
No small part of the heat issue is due to the fact that in a sealed viv, heat from lighting goes in and can't get out. In a vented viv -- that draws air in near the bottom and expels it from the top -- the heat from lighting actually increases ventilation (warm air rises) and draws the temp down.
The frog's waste is enough to fertilize plants in a viv. If a person saw rampant growth for a year that slowly tapered off over the next year, perhaps a case could be made for some sort of nutrient depletion, but I don't think that is common in vivs at all. If your plants aren't growing like gangbusters, they're not depleting anything.
You say "dirt". What is the substrate, exactly? And what water do you use in the viv? Do you use this same water for other houseplants? If tap water, what's the source (a private well, municipality). Where, roughly, do you live (certain areas of the world have tap water that is distinctly challenging to use for plants)?
Typically, people will add water to a viv (by misting) according to how much the viv and its inhabitants need (not according to the amount of water in the drainage layer). When the drainage layer gets full, you draw off that water (either through a drain, or from above using a pump or syphon or whatever you can rig up).
I think I could turn and live with animals, they are so placid and self-contain'd.