Sudden change in crawl behavior

Running Sharepoint 2013, configured for continuous crawl. I noticed a few days ago in SQL activity monitor that there were more than 50 processes running proc_MSS_GetNextCrawlBatch. I queried the MSSBatchHistory table and found that we had jumped from adding a few hundred records per day to that table to adding over 80,000 records per day. I don't see anything obviously wrong with configuration or anything that looks strange in the logs. Nobody is owning up to making any changes. Any advice? Thanks.