peppermint shrimp die off?

[Aysha]

So I bought a peppermint shrimp to deal with my aptasia about a month and a half ago. 2 weeks later he looked a bit disoriented and I heard some popping coming from the tank. I assumed my pistol shrimp had got him and moved on.

I purchased another shrimp ohhhh 6 days ago I found him unresponsive today outside of his burrow and sideways in my finger leather. He died about 10 minutes later so I fed him to my coral banded.

I have had a sexy shrimp and a coral banded in my tank since the beginning of March with no issues.

the tank inhabitants
8 hermits
3-4 snails
1 short spined urchin
1 coral banded shrimp
1 sexy shrimp
coral.

WHY DO MY PEPPERMINTS RANDOMLY DIE?
or is this normal.

78º
pH 8.1
Ammonia 0ppm
Nitrite 0ppm
Nitrate 0ppm
Phosphate.01 ppm
Salinity1.025