WARNING on Dashboard no yellow light

Im having a bit of a nightmare so hoping someone can help. Ive replaced one of my 5, 4tb Seagate drives with an 8tb. During the rebuild it failed. I then put another one in and did a straight swap (from my back up drobo) and while it took an extraordinary amount time it finally copied.

NOW, when I go onto my dash board all the drives reads “good” except the 8tb reads warning.

Im wondering is it my luck? or are the drives im putting in doing something nasty? The 4tb drives that have been running for years are 5800rpm and the new 8tb is 5400rpm, but thats the only thing I can think of that might be making a difference?

Do I need to act fast on the warning from the dashboard? Despite the yellow light NOT being on, all lights are green? Ive another drive arriving tomorrow but Id be pissed if this happened again especially after one failing already.

Both of my Drobo 5d are out of warranty.