You're probably overwatering your Philodendron Squamiferum if the leaves are dark brown or black. The roots of your Philodendron Squamiferum will rot if there isn't adequate drainage (e.g., the drainage holes are covered by clumps of dirt) or if you simply overwater each time. This implies your plant isn't getting enough water or nutrients, and the leaves will turn brown or black. Replace the wet soil with new potting mix, then cut away the roots and leaves that are the most damaged.