VM's are consuming full memory allocated eventhough guest OS is not utilizing

Hi ,

I have query regarding host memory utilization ,  we have 8 esxi hosts in cluster and one one perticular esxi host 3 vms are running and consuming all the memory allocated to Vm even though guest OS is not utilizing that much memory actively.

I set alarm for host memory utilization 75 % Warning and 85 % alert and i always recieve alert but guest OS are using only 2 to 5 % of allocated memory.

Could you please any one can suggest how to ovoide getting alerts .

Thanks in advance