50% Capacity and slow transfer rates after firmware update

I have a Drobo Generation 2 that we use at my work to hold ghost backup images, It has three 1TB drives in it. About a month ago I updated the firmware on the drobo to 1.3.5 and since then the ghost transfers are taking an incredibly long time to complete, it seems that that the update has slowed down the file transfer rate. Does this seem likely or could it be something else? Is there a way to go back to my previous firmware version I was using.

Actually I think my drobo v2 after FW 1.3.5 upgrade is faster.

My setup is (1TB+1TB+1TB+750GB).

would adding another 1TB drive make it any faster?

I would recommend Repair disk from disk utility if you are on a mac or CHKDSK in command prompt if you are on a PC.