Ficus elastica Tineke spotting
I am (relatively) new to growing plants and I have a rubber plant I bought 3 months ago. About 1/2 of the leaves (starting from the base to mid-way up the plant) have brown spots on top of the leaves. They don't rub off. On two of the leaves the browning is spreading and they are getting holes. There is a yellowing leaf at the bottom that also has brown spots.
I read the thread on variegated plants and also the one on ficus trees but I am confused about what I should do. Is it overwatering or a disease? Should I just decrease my watering and the plant will be fine, or should I trim the roots and repot it in new soil?
I keep the plant on my west-facing windowsill. From rubber plant (more pictures at the link)