Unfortunately, screen shots are not working on the Apple forums.
You might be able to see what you have posted, but no one else can see them at this time.
So, you'll need to describe things that you see in the screenshots as much as possible. Thanks.
As far as having two AirPort Express devices extend the network, that opens up a can of worms. We'll assume that you are trying to configure the Express devices to extend using a wireless connection and not wired. As you know, when you extend using wireless, about half of the potential speed on the network is lost in the process.
Adding a second Express can really complicate things and really drag down the performance of the network significantly.
It is possible to have two Expresses both connect using wireless to extend the network, but here is the rub:
1) Both Express devices need to be about the same distance from the AirPort Extreme
2) Both Expresses need to be closer to the AirPort Extreme than they are to each other
The second Express cannot extend the signal from the first Express, it must connect to the AirPort Extreme and extend that signal. If both Expresses are connecting to the AirPort Extreme and extending the AirPort Extreme signal, both Expresses will appear side by side horizontally under the AirPort Extreme in the AirPort Utility network display.
You do not want the AirPort Express devices to appear vertically, one on top of the other, in the display.
Notice that the Downstairs has a (4) in the name.
I have not ever seen that type of error, so more troubleshooting will be required.