"hanging in my kitchen for a few years now "

Probbaly Chinese made stained glass.

You might try seeing if there is a stained glass shop nearby to look over the others and check for any cracks in seams.

It looks like copper foil work.

Copper foil (AKA 'Tiffany style) sticks to the edges of the glass pieces, and then the foil is soldered together.

It has strength limits, and all the small work in the middle of the large side makes a weak spot.

It is not as strong as lead came stained glass.

If there are not any wires soldered on the inside of the glass work they should be added.
If they follow the existing seams they will not show (throw a shadow) but can strengthen the glass significantly.

Yes I have a total of 6 in my kitchen. I figured the joints were too weak for the weight of the glass. There is a shop nearby, I'm sure he an fix it.
Here's a pic of the one that fell

I'm not sure that they were specifically meant to hang in a kitchen, but they are. also they aren't really near any heat, actually the one that fell is opposite the stove. I don't have a pic with all six , but here is half on my cieling.

Have you spoken with HD? They may stand behind the Expo merchandise.

No ,Chibimimi. That's a good idea, tho. I will. I'll let you know what they say.