Samvel, you have not performed a RAID array expansion so the capacity expansion option will not be shown. You have systematically changed the drives in the array, array expansion is adding one extra drive to an existing array. I suggest that you review the following articles related to this:
Intel(R) Rapid Storage Technology (Intel(R) RST) | Adding drives to a RAID array
Intel(R) Rapid Storage Technology (Intel(R) RST) | Troubleshooting RAID migration issues