Leaf Spot Or Fluoridechlorinesalts

This sort of leaf spot can be caused by several things and without culturing in a lab it’s hard to be sure. It’s also possible with plants that what you are seeing is a combination of these problems. Here are the reasons it shows up, however, and what you can do:
1. Fungal spots. Be sure not to wet the foliage (don’t follow any advice to mist your plants) or, if you put this plant outside in the summer, to have it where the leaves get hit frequently with water. You can use an organic fungicide to help prevent fungal leaf spots.
2. Excess build up of fluoride, chlorine or fertilizer salts in the soil. This commonly happens when a houseplant is watered with “city water” that has fluoride and chlorine in it over a long period, and/or when fertilizer salts have been allowed to build up in the pot. The solution for this is to repot the plant, gently removing some of the old potting mix from the roots and putting the plant back in a clean pot with new potting soil. Do not put rocks, shards or other materials in the bottom of the pot no matter where you’ve read that information: it’s bad for plants. After that, water with distilled or well water that doesn’t have fluoride or chlorine in it. Use an organic fertilizer in the future according to directions.