Thanks for the photo. Those tiny things are spider mites and they have caused the mottled appearance on the leaves.
Because so many of the leaves are mottled, it means the infestation is widespread.
If you want to try to salvage the plant understand that the leaf discoloration is permanent and will remain even after the mites are treated. You should consider cutting back many of the taller, overgrown stems and discarding them. The more you cut off, the fewer mites you will have to treat.
Pruned stems will usually regrow starting just below where the pruning cut is made.
After pruning, fill your sink with soapy water and slosh all of the remaining stems and their leaves in the soapy water for a minute or two. The object is to make direct soap contact with every last tiny spider mite. If you are thorough, a single treatment should be sufficient.