I'm pretty overwhelmed here.... It was extremely easy to set up my RAID but it turns out one of the 4 drives is bad. Seems the GUI doesn't do much more than build RAIDs. I've been messing with various commands to remove the defective disk and replace it with a new one. I am totally at a loss on what to do.
I need to remove /dev/sde and replace it with /dev/sdb after it reboots. When I fail sde and remove it, the array says it isn't mounted. I'm not particularly handy with linux but I can google stuff. My googling has turned up a hundred different weird scenarios but not a hand-holding guide.
At the very least I managed to undo whatever dumb stuff I did by adding the damaged drive back to the array. It still works but it's getting SMART errors so I need to replace it.