Hi! I like your setup!
I'm by no means experienced with aquaria yet, so I can't help you with anything below the water level. However, I know there are some nice threads on other parts of the forum for light cycle and what have you. For the fungus there are a lot of threads like this: https://www.plantedtank.net/forums/8-...ls-tubing.html
As for pH, I know that platys are usually referenced as liking a pH between 7-8 or 6.5-8.5 depending on where I have read about them, so they would be okay at 7, I would think. The pH for your aquatic plants depend on your species list, from what little I know. But if your tank has survived this long, you're probably doing better than I will when I start my first planted tank!
Anyway, I've got a experience with terraria and potted houseplants, so I may be able to give you some things to consider with your Adiatum sp.
maidenhair fern (the plant in the last pic):
Are you certain the growth is slow? Maidenhair usually take a while to grow. If you're sure:
What is the substrate pH for the maidenhair? Most maidenhairs prefer their substrate to be on the lower side(5.5-6.5 pH). Did you change it from the substrate it came in, or did you use what it grew in? From my experience, they can survive higher pH, and you may be better off keeping it in that substrate, since they don't like having their roots jostled, but it may be leading to slow growth.
Has it had fronds drying out and dying, that you have cut back? Any brown spots? Sometimes over-watering will cause them to get brown areas. Under-watering will lead to dried out fronds, though that is unlikely to be an issue if you have it constantly being hit with water. I've seen it stated that they like to have the top inch of their soil dry out on the GardenWeb forums. My experience is similar, but I keep mine in low-light.
Is it getting crunchy on the tips? It may be too close to the light. Most maidenhairs prefer medium light levels.
How humid is your setup? My maidenhairs thrive in the summer (70% humidity) and suffer in the winter (30% humidity). Usually ones in enclosed terrariums have no problems with -low- humidity, but since your paludarium is open, it -might- be an issue (I'd say it's unlikely, but I figured you know your setup better than I do
I've read one reference to the feasibility of maidenhairs being grown hydroponically. Here it is: https://books.google.com/books?id=Wz...oponic&f=false
Anyway, I hope this helps!