I agree that mollies are not going to like most of the things that will stain one's water. If you want to use something, in thar area, as a med. I would choose the rooibos tea because it will more likely raise the pH by .1 or .2 amd it has the most anitbitic/antioxident properties than anything else below in this respect. But the mollies will like the salt. Whether that might help is another issues.
As one who does a stained tank I can offer some info. Firstly, I use almond leaves, alder cones and brewed rooibos tea. The tea does the most to help with the staining and the medicinal properties. The leaves help with the staining and their med value and the alder cones help with staining and lowering the pH. But if I need to drop the pH for a water change, I will add muriatic acid to the changing water and or the tank.
Rooibos tea (meaning red bush in Afrikaans and pronounced roy + boss) has nothing to do with traditional tea, which comes from the Chinese plant Camellia sinensis in the family Rosaceae. Rooibos comes from the plant, Aspalathus linearis, a legume in the family Fabaceae- it is related to peas and beans. The bush is more like a broom than a bush. The top of the bush is cut off, dried and oxidized before packing in tea bags or sold as loose tea..........
"For fish keeping we are interested in the plant phenolic compounds that act as antioxidants and also as antibacterials (it won’t harm filters). This is similar to the humic acids found in natural “tea” stained water. Oak leaves contain a lot of the plant phenolic quercetin (from the Latin name for the oak tree, Quercus robur) and rooibos also contains some quercetin plus the compound aspalathin, which is closely related to quercetin......
Research at the University of Stellenbosch shows that rooibos also has natural stress relieving properties. It is entirely safe to use and is beneficial for keepers and fish alike."
Most of the research I have read indicates there are minimal tannins released by rooibos. It also does not contain caffeine.