Hi, I've has this heart leaf philodendron for several years and it's always done really well. It is up for a repotting. I've been giving it rainwater from the monsoons and a little fertilizer lately and it has had more new growth lately. However, I noticed today some leaves were falling off and after inspection, found that one section, several stems were shriveling up. It seems localized even though they are different stems. Is it some sort of pest? It was hidden under some broad leaves. Can this happen if the section isn't getting enough light? I've had this plant for a long time and I don't want it to go downhill! Thanks.