I recently started collecting tropical house plants. some of the lower stems of my split leaf philodendron are turning yellow, i try and moderate the amount of water i give my plants and I also have them in clay pots. I am not sure if the cause is over watering, nitrogen deficiency or am i dealing with some kind of pest or disease. I want to get to the root of this before it gets to the leaves. I keep her on a west facing window with indirect light. Also there is little bit of browning on the edge of one of the leaves, I was wondering if this is because of using tap water(we have flouride in our water). I would really appreciate some help.