From my knowledge, when swords have a leaf die it will not grow that leaf back. So for your brown leaves cut it off as low as you can, the plant has given up on that leaf.
If you just put that sword in there then its not uncommon for it to drop a few leaves. The lighting on the fluval is more than enough for the sword (I have it). If the plant is sitting up at the top of the water turning brown it is not from the LED
"burning" the plant. LEDs dont produce enough heat to burn plants in most situations, thats one of the benefits of LEDs.
Yes most swords will get very big, tha amazon sword is one of the biggest, but I feel you wanting some swords. Look into micros swords as suggested (though they look more like grass), or one of my favorites is the melon swords, Rosette (can get it at petsmart), compacta, or queen.
I have amazon, melon, rosettes, compactas; the melon and rose dont get nearly as large and have great looks. My personal favorite sword is the melon, it has a nice red hint to it.
Marble queen- https://www.azgardens.com/product/lo...n-sword-plant/
Most, if not all swords (and other plants) will require frequent trimming in a tank that small. Buy what you want, learn how to take care of it and how to prune it, be happy.