What sort of light do you have on the tank and how long is the light on for?
Do you use or have you ever used an algicide (something to kill algae)?
Algicides also kill higher plants.
Most aquatic plants need lots of light. If they aren't getting enough light, they won't grow. A bit of iron based aquarium plant fertiliser can also help but light is the big one for plants.
Most aquarium plants like a bit of light and if you only have the light on for a couple of hours a day, they struggle. If the light doesn't have a high enough wattage they also struggle. Try having the tank lights on for 10-12 hours a day. You can have light son for up to 16 hours a day but the fish and plants need 8 hours of darkness to rest.
If you get lots of green algae then reduce the light by an hour a day and monitor the algae over the next 2 weeks.
If you don't get any green algae on the glass then increase the lighting period by an hour and monitor it.
If you get a small amount of green algae then the lighting time is about right.
Some plants will close their leaves up when they have had sufficient light. Ambulia, Hygrophilas and a few others close their top set of leaves first, then the next set and so on down the stem. When you see this happening, wait an hour after the leaves have closed up against the stem and then turn lights off. It's worth investing in a couple of these plants just to see how they do. They are generally good in most aquariums and give you a rough idea of if you have enough light on the tank.
Plant lights should have equal amount of red and blue light and a bit less green light.
TURNING LIGHTS ON AND OFF
Stress from tank lights coming on when the room is dark can be an issue. Fish don't have eyelids and don't tolerate going from complete dark to bright light (or vice versa) instantly.
In the morning open the curtains or turn the room light on at least 30 minutes (or more) before turning the tank light on. This will reduce the stress on the fish and they won't go from a dark tank to a bright tank instantly.
At night turn the room light on and then turn the tank light off. Wait at least 30 minutes (or more) before turning the room light out. This allows the fish to settle down for the night instead of going from a brightly lit tank to complete darkness instantly.
Try to have the lights on at the same time each day. Use a timer if possible.
IRON BASED PLANT FERTILISER
If you add an iron based aquarium plant fertiliser, it will help most aquarium plants do well. The liquid iron based aquarium plant fertilisers tend to be better than the tablet forms, although you can push the tablets under the roots of plants and that works well.
You use an iron (Fe
) test kit to monitor iron levels and keep them at 1mg/l (1ppm).
I used Sera Florena liquid plant fertiliser but there are other brands too.