Sand and gravel differ mainly in the particle size. Both are pretty inert. If you want serious plant growth, using a plant specific substrate works better. Flourite, for example or Eco complete. Adding gravel to sand just results in sand on the bottom, as it sifts through the bigger particles.
I have a planted, mostly shrimp, 10G tank with Moonsand in it. Totally inert, but using ferts & Excel, everything in it grows like mad. Only thing not doing great is the crypt, because it does need root tabs, which I must get for it.
From the pics, at least some of your anacharis looks like it is putting on some healthy new growth, with larger leaves, so that's a good thing. I don't have the best luck with it here, because the rooms have become too warm. So the tanks have become too warm and the plant likes it cool. I need to start the fans running again.
I have a tank being cared for by a pal, in a much colder home, and anacharis in that one is doing fine. It gets only daylight from a window and whatever the fish contribute. Mostly it's floating, though the substrate is Eco Complete. Just didn't bother to plant it when I moved the tank over there. Because of the low light and no ferts, it doesn't really grow that much, but all of it is very lush and thick.
That tank is running at around 72 most of the time, sometimes slightly under 70, if my pal forgets to close the patio door. He tries his best, he's not a fish guy, but has kept the fish alive for most of this year for me, so I can't complain ! The fish are cooler water species and are managing, though I will be glad to get them home, if the landlord ever finishes the repairs that need doing.
If you can give yours some cooler temps and some ferts, I think your plants will improve.
I have one stem of it in one of my warmer tanks here. I use Excel and Flourish liquid ferts, and it was planted in the Moonsand. It grew about six inches in about six weeks. But it's not nearly as thick and lush looking as the stuff in the colder tank is. Nice 'n green, just thinner than it should be. I think that's the warm water. The lighting is nuts, I keep them on much longer than normal, quite purposefully, to grow algae for my Otos.
In tanks, plants do not have the resources available that they would have wherever they grow natively. So we have to provide some extras. Carbon for one, [ the Excel helps with that], because the only carbon in water is the CO2, which is very quickly depleted. And in habitat, food and light is usually pretty close to the ideal for the plant, or it wouldn't grow there. So expecting to get lush growth in a tank, without using some extras, is not very likely to be successful.