Are you adding fertiliser or nutrients? Remember that a lot of the nutrients your plants need are being provided by fish waste in aquariums. In particular im thinking of nitrogen and phosphate.
In aquariums, nitrogen is supplied through ammonia and nitrate. With no fish in the tank these nutrients could essentially be zero unless your tap water contains nitrate or your fertiliser has an appreciable amount of nitrate in it. Even if you are using a fertiliser, most aquarium specific fertilisers have essentially zero nitrogen or phosphate in them because they are seen as causing algae. A few aquarium fertilisers do have these essential nutrients in good supply though. NA Thrive is often considered the #1 aquarium plant fertiliser, and it has a good amount of nitrogen in there. If you are from a country where NA Thrive is available thats a good fertiliser to go for. I think a standard dose of thrive increases nitrate by 6ppm. Here in the UK we have TNC Complete, Aquarium Coop and Tropica also do all in one fertiliser that has a good amount of nitrogen and phosphate in them, there will be other products too. Or use non aquatic plant food. Or use water from your aquarium taken before a water change.
Pothos and those floating plants are very nutrient intensive, and even if there is nitrogen and phosphate in the water source the pothos will take it all up and starve the other other plants.
Then there is light. Most aquariums have a good, strong light immediately above them. How is the lighting for your vases.
Plants need CO2. Gas exchange is promoted by surface agitation, so if there is no water movement CO2 cant be replenished. Not sure how much of a problem this would cause, i would have thought regular water changes would solve this. Same for carbonate hardness. Most of those commonly kept, low demand aquatic plants actually get their carbon needs from carbonate hardness, not disolved CO2. Carbonate hardness hardness will get used up as the plants grow, but regular water changes should replenish this.
Are you dechlorinating the water. Chlorine can burn plants.
Im interested in how this goes for you. Im planning on making some moss balls in a jar to give at Christmas presents with a short note on "keeping your moss ball healthy". They are really expensive to buy, but i think i can make them up quite cheaply. Im shortly going to do one as a prototype to see how it goes long term. My plan is to keep the jar somewhere well lit, change the water every 2 weeks after the new water has sat in a jug overnight to dechlorinate it. See how it goes. Hoping they wont need fertiliser.
