Does mdstat showing very different block sizes for identical drives indicate a failing drive?

One of my servers has a RAID1 array composed of two 240GB SSDs. It is managed/controlled via Linux, not via a hardware card.

Recently, for no apparent reason, the array needed rebuilding. I rebooted the server a few times recently, so perhaps there was a failed shutdown that forced it.

However, the rebuild took significantly longer than expected (~5 days), which makes me wonder if one of the drives is failing.

cat /proc/mdstat shows:

root@i3261:~# cat /proc/mdstat
Personalities : [linear] [multipath] [raid0] [raid1] [raid6] [raid5] [raid4] [raid10]
md0 : active raid1 sdb1[1] sda1[0]
      242153280 blocks super 1.2 [2/2] [UU]

md1 : active raid1 sdb5[1] sda5[0]
      7768000 blocks super 1.2 [2/2] [UU]

unused devices: <none>

The delta between the blocks seems very high. Especially since these SSDs are supposedly identical.

Does this indicate a drive failing?