Leaves curling on tips of java fern

[Phish]

I have a very large java fern in my tank. It has recently been relocated. The tips of the leafs are starting to curl downwards.

I have a low, low-med light tank, use flourish, flourish potassium and flourish excel. The rest of my plants do and have been doing A-okay under these conditions for quite some time.

Thank you for any suggestions, I can send pics if needed.