Thanks. If they are melting you may need more light. Often times the stock fixture may not be enough to support plant growth but other in most cases they are fine.
I would hang fire on the light for the time being. After all it’s only been two weeks. Also just remember that as the plants begin to grow the requirements for nutrients and your liquid co2 will too. You can try upping the fertilisers a tad to see if the melting improves.
When my swords were very transparent it was the liquid co2 that made the difference but some plants do take time to ‘graft in’ new leaves. I’ve seen the same transitional period on dwarf sag (Sagittaria Subulata) the first underwater leaves look see through and you can almost see the individual ‘strands’ of tissue in the leaf but they progressively fill in with each new leaf until they begin to look healthy.
You could also try adding more liquid co2 *but be careful it is toxic in large concentrations* and see if things improve. In the tank above I was using both ‘liquid’ and gas forms of carbon dioxide.
Lastly, have a look again at the sword plants on the left in the picture above picture. When this was first planted it looked very much like your plant with the large waxy, oval shaped leaves on long stems so you can see just how different the leaves are when grown emersed as opposed to submerged. Your amazon sword plant was grown emersed so the initial leaves may not be perfect. Just have a little more patience