I have been debating this for a while, that is, fertilizer use with such animals.
First, perlite is just used as a additive to create more aeration in soil. Chams do have a possibility of ingesting it. I have seen dehydrated chams die with mouthfuls of soil. Hard to say exactly what was going on there, but thats another issue outside of simple soil component exposure.
I have used potted plants with exposed soil tops for years, with perlite and granulated slow release fertilizer. I have had no issues myself (that was observed..).
I think for everyone to keep things simple and safe, just repotting your plants in an organic potting medium, rich in natural material, should be the only thing really done. Repotting plants every year or so in humic rich organic soil would probably be safest.
I have a bio-organic fertilizer mix I use on my ornamental and house plants as a foliar spray. It contains natural components, combining a balance of trace elements, minerals, and micronutrients. I am considering using it on my cage plants (mostly Ficus spp and Schefflera), but need to do some more research. I am also considering using seaweed extract, and or fish emulsion. Certainly, I think you would be safe using worm tea or siphoned waste water from freshwater fish tanks, provided you had not dosed recently with malachite green, copper, or any other such substance.
I am sure there are numerous posts on the matter, that of which I have not yet looked into. I would not recommend using anything other than pure worm tea, fish emulsion, or fish waste water.. unless you feel entirely confident you understand the dynamics of what the plants need, and how the applicants could affect your animals.
As far as what happens to your plants, the most common thing I see if loss of foliage (likely, mostly as a result of infrequent watering+small pot sizes), and yellowing leaves. As plants lose nutrients, they become chlorotic and begin to develop yellow spotting. A humic rich additive such as fish emulsion, is typically going to be high in nitrogen. Nitrogen is what is mostly used by the plant for vegetative growth. Semi-regular use of such a product could prove beneficial if the proper precautions were taken.
Keep in mind how your feeders respond as well. If they consume plant material; drink water from the saucer or the moist soil; climb in the pot and when consumed by chams, pull substrate with them; etc etc etc.
Perhaps one of the best things one could do to maintain good looking and filled out plants, would be to have doubles for each or several cages. You could cycle plants out and dose a mild nutrient load of some type while the plants were in a window. Then change out for the cage plants.
Hibiscus in particular can be a little difficult when trying to grow in a cage. Whatever issues you are experiencing, are likely not related to fertilizer. I can somewhat maintain Hibiscus in a cage, but in our greenhouse, they have anywhere from three to ten blooms on them at any given time. I would guess watering and light levels may be your problem.
All aside, there are many different opinions on how to handle soil mixes, and plant care with herps (esp chameleons). Some people prefer to use fake plants with no soil, some cover the soil with cut plastic, some simply buy home depot plants and change them out once or twice a year. I personally like the challenge of trying to keep a plant at it's best inside the cages. I feel for myself, a semi-frequent low dose organic fertilizer should keep my plants full and green. I will likely also switch plants out periodically and allow them to spend a month or two outside, where they can really green up quick.
Perhaps someone that has finished all their organic chemistry classes can chime in. Lol.
Zach