with indian fern, don't let the fish pick at the roots, make sure all the roots are underground, my old one died because the tetra picked at the roots a lot.
true, the same with ph, most fish can go in many ph ranges but are best if they are suddenly put into a different one. At least thats what my fish are like....
stop feeding, I had this before and stopped feeding for a few days, and did a water change. Just don't do too many water changes, too many brought my ammonia up.