missing shrimps

[leesst200]

I have kept 4 shrimps for a couple of years until now i only have 2.
The shrimps were peppermint, camel, cleaner and blood red.
They have all been fine until now the cleaner and peppermint are missing.
They are definatley not there (removed all rocks to find them).
What is the likley explanation?
Would they have been fighting?

 

[FluffynTex]

Most shrimp that I am familiar with have approx 2 year life span. Perhaps their time is up?

 

[leesst200]

thats probably it then, I have had them around 2 years.