Upgrading a drive

I've got a Raid 5, which originally was 3 x 2TB disks - One disk failed, so I replaced it with a 4TB thinking thinking that at some stage I could upgrade the others to give me more space. I bought a couple of new disks about 6 months ago so thought about time to upgrade another disk, then after rebuild the last disk and then grow it. Problem is, if I just rip out the disk then the raid management then shows nothing at all, so I can't rebuild or do anything? After some advise - Current detail of raid below:-

Version : 1.2
Creation Time : Mon Dec 31 11:54:40 2012
Raid Level : raid5
Array Size : 3907025920 (3726.03 GiB 4000.79 GB)
Used Dev Size : 1953512960 (1863.02 GiB 2000.40 GB)
Raid Devices : 3
Total Devices : 3
Persistence : Superblock is persistent


Update Time : Wed Oct 21 21:26:44 2020
State : clean
Active Devices : 3
Working Devices : 3
Failed Devices : 0
Spare Devices : 0


Layout : left-symmetric
Chunk Size : 512K


Name : CowShed:Udders
UUID : 1c5ae26a:1c6abeac:888454b5:02badf80
Events : 19847

Number Major Minor RaidDevice State

0 8 16 0 active sync /dev/sdb

3 8 32 1 active sync /dev/sdc

2 8 48 2 active sync /dev/sdd

Think I have this sorted - first fail the dick

mdadm --manage /dev/mdXXX --fail /dev/sdX

Where XXX is the raid IS and X is the disk ID - in my case "127" and "d" - This put the raid into a failed state, shut down the system, replaced the disk, then ran the recovery to rebuild.