One of my plants is dying all of the sudden, leaves are NOT becoming transparent but holes are appearing in them and then i pluck the dead stems out and they basically fall out of the substrate. Only one type of plant is affected. I think it's probably just that this plany can't take the mid 80 degree heat anymore. It is a Red Melon Sword (echinodorus barthii) and they can tolerate temps up to 82. Antyhing else it could be?