Google Scholar reflects the state of the web as it is currently visible to their search robots and to the majority of users.

If your citation counts have gone down, either your paper or papers that cite it have disappeared from the web entirely, or are unavailable to the search robots, or, perhaps, have been reformatted in a way that made it difficult for Google Scholar's automated software to identify their bibliographic data and references.

If you wish to correct this, you need to identify the specific documents with indexing problems and ask your publisher to fix them. Please refer to the technical guidelines.