Aquatic plants take weeks to get used to new tank conditions. It's natural for them to look poorly and die back. After some time, new growth will start, typically from the small, black areas on the back of the original plant.
Java fern is a slow grower, that doesn't require high end lighting or expensive commercial fertilizers. I have this plant in subdued light and no fertilizers other than what the fish produce and it grows fine.
I'd suggest giving the new plant some time to get used to your tank water and back off all the fertilizers. Keep the tank water pure with large, frequent water changes. Changing half the water every week to 10 days will give you the best chance for success with the fish and plants.
Just a thought.
"Fear not, my young apprentice. Just change the tank water."