What do people recommend for an affordable light for growing plants in aquariums?
And what size?What do people recommend for an affordable light for growing plants in aquariums?

So the plant is rotala rotundifolia. What liquid ferts specifically are you dosing? What ones did you add to the substrate cups?
Any of the lighting options I mentioned above would work.... also for a 10 gallon you could also get a desk lamp/shop light with a cfl bulb.... look for a color temp of 6500.
Rotala is a difficult plant but OP's plants look more like Hygrophila polysperma to me.
The light should come from the top (change the hood to a glass top) or else the plants will grow (if they grow...) toward the light, sideways. A photoperiod of 14 hours is way too long; you cannot compensate low intensity light with a longer photoperiod.
Airstones do not add CO2.
What fertilizer pellets did you add in the jar?
