How long have you had the plant in your tank?
Was it from emerged or submersed?
If its new to you and it has been an immersed plant. Then this is very normal. Nothing to panic about. Prune out the leaves that are effected. Over a short period, you will have removed all non aquatic leafs, in which time the plant should of been producing fully aquatic leaves, then you will have a stunning plant.
Good luck!