It looks as though you may have a couple problems. One photograph shows what looks like scale, a common insect pest of houseplants, although it is difficult to see for sure. Visit this
link and find the image of scale insects near the bottom of the page. They are difficult to recognize as insects because they are immobile. Look closely. It looks like you may have a severe infestation. It will be difficult to get rid of them. You can attempt to wipe them off using a cotton swab dipped in rubbing alcohol, or a cotton ball. If the infestation is severe you may have to remove the infested leaves, leaving the smaller, new leaves. Remove any scale on these leaves and keep a close eye for hatching eggs.
It also appears as though you also have leaf spot. Allow the plant to dry out between watering. The infected leaves will not turn green. If these leaves are removed (along with the scale), and proper watering procedures are followed, the new leaves are less likely to have this problem.
Raakel
