I have an Amazon Sword in a Fluval View 4 gallon tank with a betta and a snail (and some Java moss and an anubias nana).
The tank is a couple of feet from a large south-facing bay window, and it has a built-in set of LED lights.
For almost a week now the sword's leaves have been turning translucent; other leaves (green ones it seems, rather than the translucent ones) have had holes in them.
About a week ago--I don't recall if I did this before or after I saw the translucent leaves--I put in a single API root tab (which started to disintegrate the moment it touched the water) near the roots, and another two days ago. No change noticed.
If it's still a nutrition issue, I think I'd like to go with something other than the API tabs. They've been falling apart almost before I can get them into the gravel, and the water turns green-brown (I've done 50% changes to clear it).