EX4 expand raid5

Hello, i have this WD EX4 with 4 x 2 giga tera disk in RAID_5 resulting in an almost 6 tera share.
After years It’s almost full.
Can i expand the space by buying 4 new bigger disks and substituting the disks one by one ?

Hello,

Please refer to the following KBA article: http://support-en.wd.com/app/answers/detail/a_id/27421/