Plate shards on SRS are rare drop for long time ago, belive me. I run SRS on Yin for months after other updates too. First we got lots of shards, than the drop was random, 1 plate shard after another after 20 rounds. Above 20 rounds in a row with no shards. 3 rounds than a shard. 5 rounds than a shard. Same with red marble. Maybe the drop is in the category rare for now.