Why is your plant so small for being 3 months old? It should be almost full grown and ready for cycle...
Secondly, you are using fish tank water.. I've thought about this myself seeing as I have an 80 gal full of cichlids pooping constantly, however, you dont really know the concentration of the nitrogen and what else you are giving the plant.
Im seeing tiny lil yellowish edges starting on the leaves in your first pic. Either over watering, or too many nutes as far as i know, and the leaf tips curling down would also confirm the overwatering.
If i were you.. I would just let the plant do its thing for awhile, leave it alone, let it bounce back and when you start seeing some more rapid growth and difference in the leaf behaviour, start back with water/nutes, and maybe use nutes you know the concentrations of.
Cant really tell how moist your substrate is from the pictures, but I sort of wanna say its pretty wet.