Yes, return them. No way to tell without seeing them if it is bacterial or a fungus but you don't want either. You'll find a couple of related discussions currently running over on the Growing Tomatoes forum. Best to start with healthy plants. ;) Dave

My jade has these black spots too. It is a baby jade my friend gave me (first one for me!)about an inch tall with 4 leaves and 2 tiny leaves at the top. After I transplanted it I didn't want to water it for a long time because I read the roots need to heal first, right? So, I kept it inside because it's been raining every day here in Florida. Then after about a week and a half inside, I put it outside. It got one heavy rain, but I have it in well-draining cactus soil, so assumed that was okay. It gets FULL FULL sun all day outside. After about another week outside I noticed all of my succulents that I had recently transplanted and moved inside and outside with this plant looked sunburned. It is weird to think this could happen to a desert plant, but they did. My aloe had red tan lines where the upper leaves blocked the lower leaves. A baby aloe I just moved to its own pot turned brown and squishy. Luckily, I moved it back inside and watered and it came back to a healthy green. Anyway, this after this sunburning, my jade leaves got a litte bumpy. They're still hard but they aren't waxy looking like I've seen on big jades. Then they developed these brown spots. Could this be from the sun. The spots look like they are part of the leaf and not a fungus. Sorry about such a long question, any ideas?

I picked up a couple of Zz 'Raven', and I am really happy to have this nice variation. The color is much darker much sooner if they get a bit of direct sun. I also have other forms; one I like has a much more round leaflet, and I also have the two dwarf varieties. I have had various variegated ones, but they aren't stable.

That type of yellowing can be caused by a magnesium deficiency. Have you been fertilising it?