Repartitioning Time Machine by reallocating excess storage from other partitions

I have three partitions on my Drobo. Two partitions with a max of 17TB and one working as a Time Machine partition with 8TB. The T-M needs to be larger. Since I don’t use all the storage in either of the large partitions, I would like to allocate more storage to my Time Machine by reducing the size of the other two. Can I reallocate without losing data. Can that be done? And if so, how.