Ok, that makes more sense. I think you have far too many shards, and your cluster performance is suffering as a result. It is worth reading this article:
Aim to keep the average shard size between at least a few GB and a few tens of GB. For use-cases with time-based data, it is common to see shards between 20GB and 40GB in size.
If you generate 400MB per day, split across 5 primaries, then each shard must be ~80MB, which is ~500x smaller than the recommended size. I think it would be better to have a single primary in each index, and to use monthly indices rather than daily ones. This will enormously reduce your shard count and you should see better performance as a consequence.