the emergent (not the wisteria) is actually red mangrove. So its not fully aquatic, i guess its technically not "emergent". By capsules, do you mean micro? CSM+B is what I dose. I usually dose right into water column, I add root tabs once in a while. I feel that my issue is urgent, and am not sure if root tab will be noticeable quickly.
I agree, root tabs I meant with macro and micro nutrients, slow release, osmocote type, absolutely take real time to impact, and patience with plants is often key. Rarely is plant care an urgent matter. Plants can't have heart attacks, though obviously sticking a tropical plant out in the frost will kill it, but most problems with plants are best thought of, if we are going down the path of medical analogy, which I am, like non-aggressive cancers, slow.
I only act fast for issues that put my fish and shrimps in danger, low oxygen, high temperature, pathogens and excessive CO2.
Plants are seasonal and rarely are a risk from short term factors, even if I am on holiday and my son forgets to open the curtains for few days so long as it isn't for a prolonged period, the house plants recover, or almost recover, before I get home.
Foliar feeding in the garden in the summer, works very quickly, and only works during the growing season peak, the effects of foliar feeding can sometimes be seen in days, water column dosing in the tank is much the same in timescale, but as in the garden it is easy to do more harm than good with a foliar feed. And further, a fish tank is not hydroponics, to state the obvious, the leaves are in the water, so attempts at quick water feeding solutions often favour algae if light and CO2 are deficient or light is excessive, normally duration not intensity, with of course, some exceptions for shade loving plants.
A good dose of Potassium will not excessively encourage algae (but with slow growing plants any 'fix' will take time to become apparent) however, if lack of Potassium is the issue it will be utilised by the epiphyte plants so long as there is an adequate total amount of other macro nutrients and trace elements. Adequate of course and excessive are important terms and it is ever so easy to overdo nutrients, especially macro nutrients. I have certainly added macro fertiliser to see Nitrate rise from <10ppm to >80 and then have to do a 50% water change, everyday for several days to prevent an algae soup developing. Slowly slowly catchy monkey.
Thank you for telling me the plant is a Mangrove, high humidity is needed, as the plant reaches further from the evaporation at the meniscus/surface water level and closer to the light, it is, I suspect, drying out. Mangroves strictly speaking are actually emergent, woody and do grow leaves underwater but they tend to shed them as they increase their total volume of atmospheric leaves, Red Mangroves do well in freshwater, but they need lots of intense light so take care dialling down your lights. You might consider an ultrasound mist maker. I keep meaning to get one myself, my Bacopa, Indian Fern and Ludwigia dry out at the tips once they get a few inches above the top of the tank.
You said your floating plants are healthy, therefore you are doing almost everything to create the right conditions.
Good luck.
