Brand ew disks turns led solid red in my EX4100 after finishing the start up process

Hello, I bougth two disk to expand the capacity of memory of my EX4100, I shut down the device to install the two disk, at start again, during the process of star up the two disk where led blue, aftter the whole process, the led of the new disk turn it solid red, when I get into the home screen in the browser, only the disk that I had previously installed where recognized, the amount of space was the same that I had. the two new disk was recognized In the disk status screen, so the device know that they are installed, but I can’t acess to them to format it in the utilities screen.

The previous installed disk are formated as jobd a separate volumes, and they are WDC WD40EFRX-68N32N0 models, the new one are two RED WD40EFAX-68JH4NO. All are 4tb, all WD.

I’m using the OS5, and have the latest version of firmware.

¿There’s a way to know if the disk are bad?

¿The two model are compatible or I have to got the same model in all bays?

¿I have to have formated all the disks with the same RAID profile to be able to use them in the Device or I can use diferent RAID types working togheter?

I’ts recommendable to back up the info, and format all the disks?

If some one can give me some feed back, I’ll apreciate it a lot.

Thakns you.