Interveinal chlorosis in F elastica (if we're even talking about THAT rubber tree) is often an iron deficiency related to high soil/ irrigation water pH levels and can often be remedied by acidifying irrigation water to a pH of about 5.5 using white vinegar or citric acid.
If the problem is indeed veinal chlorosis it could be an indication that there are serious protracted nutritional issues or conditions in the root zone affecting the plant's ability to synthesize chlorophyll. Usually, limited availability of one or more of nitrogen, iron, and magnesium are involved.
If you haven't been fertilizing lately, and without any information to suggest otherwise, Occam's Razor would lead you to the idea that flushing the soil and fertilizing would be the next logical step. If you HAVE been keeping up on your nutritional supplementation, more information will be needed about your care regimen if we're to be guided down a logical path. The potential causes of 'chlorosis' are many, but the answer more often than not will be found to be something amiss in the root zone ..... too much/little water or air, low fertility, soil compaction, root congestion, leaves are in the process of being shed for any of a variety of reasons, pH, high soil temps, ..... .
Al
