Losing 52 SR with one game less than 50% win rate means you’re losing more than you’re gaining per loss / win. That means the PBSR is telling you that your statistics (not sure which ones) are below the average of the rest of the people playing that hero in the tier. The normal SR gain / loss is 24. Anything higher on a loss means you’re below average statistically, and anything higher on a win means you’re above average statistically.
I highly recommend you use Basilisk’s Overwatch Performance Tracker spreadsheet to record the results of your matches, as well as reviewing the matches with the new replay feature to see what the other support heroes are doing differently than you, or to figure out where you were when you died.
Details are in here: