VNX/Datamover/Memory upgrade?

We have some VNX5400, they are about 2 years into usage, we use them as a target to migrate from various legacy storage platforms (and it is a backup target).

2X datamovers, 33 file systems, 28 replications (mostly VMware NFS datastores, some CIFS)

Memory usage now over 85%, slowly growing over time as usage increased, therefore do not think a memory leak is involved...

Is it possible to UPGRADE the actual amount of MEMORY in the datamover?

or

Do we need to get a new pair of datamovers and split the file systems?

greater MEMORY size?

Thanks.