A photo of the problem would be helpful, not least to establish which 'rubber plant' you mean - sounds more like Ficus benjamina than an actual Rubber Plant (Ficus elastica). Check the stems and leaves for signs of infestation by insects, including scale. I'd also ask how long it's been in the same pot and same compost, and whether it has, in the last 2 or 3 months, been waterlogged?

Hi,
Thanks for your reply. I believe it is a ficus elastica, based on my research as it looks idendical and in its prime has been very bushy with large glossy leaves. It has certainly not been water logged - I have if anything neglected it. It has been in the same pot and compost for 5 years, but does have drainage in the bottom of it and I have tended to fed it with baby bio occasionally. I acquired the plant 13 years ago and it was a large plantt hen, so I have no idea how old it is. I haven't spotted any insects, what would this look like?
It is in a sunny spot in our bay window, which is also drafty and cold this time of year - could this be the problem?? It normally does drop a few leaves this time of year but never this many. Even the leaves which are not spotted and look healthy are very droopy. I have added a photo.

Its that very description of 'bushy' which makes me think it's not Ficus elastica - these usually get extremely tall (after the number of years you've had it, I'd expect it to be 9/10 feet at least or more by now) and have either one or two main stems with very large leaves coming off, so bushy isn't a word you'd use to describe it.
Scale looks like little shields attached to the woody parts, but if you have it near a draft, it will be that - if, as I still believe, it's Ficus benjamina or a cultivar of, then they will not tolerate drafts and cold air, so that's the likely cause. Most houseplants will react badly to that, but Ficus especially so.

Anyone wishing to see the photo .. it is on the main photos page. [Garden Pictures]

Hi. Thank you for your help again. I have looked up Benjamin Elastica and it certainly appears different to me. The leaves of my plant are about 20 cm in length. I have trimmed large chunks off it with loppers each year to keep it under control. Anyway, I will try moving it's location and see if that helps.

20cm in length, probably is Ficus elastica - out of drafts would be good though.