Drive Red but when replaced all are flashing yellow and green

Drobo FSB800 working slow, noticed one drive was red. Purchased a new drive to replace it. Upon install the new drive showed green and all worked good for 24 hours. Now another drive is red and all 7 others keep flashing green and yellow. I see from reading about this it could be that we have just filled it up. The dashboard shows that storage is full. Assuming all the drives are full, do I take them all out and replace all of them or am I looking at “bad” drives too? To increase space by creating an archive I think I need to replce all drives. If space is the problem what is the solution at this point? Take some content off the current drives so I can create an archive as right now unit is not working properly. Would I put back the “bad drive” to keep in the archive set? Then should I replace all drives to capture new content? Any help would be appreciated.

Is it flashing red, or solid red?
Flashing red indicates a failed drive, and Drobo would try to rebuild using the existing drives, reducing protected storage capacity in turn (so it will appear to be more full). If not enough storage available to re-establish protection, then it will give you a critical warning.

If you do not already have a backup of your data, you should make a copy of the data ASAP.