Variety? There are several white cucumber varieties, a couple of which are short and dumpy. They turn yellow when ripe. poor pollination results in misshapes.

For what it's worth, the package showed long green cucumbers. I don't remember the actual variety other than they were supposedly burpless.

All cukes start to turn yellow when over-ripe, but yours seem to be doing so early on. Assuming these are supposed to be green cukes, I believe poor watering (too much or too little) and also poor soil quality, as in, nutrition-wise, can result in that. You might want to hit them with some ferts. Cucumbers have shallow roots, so keeping the soil moist is important. If you have yellowed and or mottled leaves as well, mosaic virus could be an issue.

That looks like a lemon cucumber.

I think lemon cucumbers start out green and eventually mature to yellow. That's not the story here.

I've had a whole vine do this on a healthy plant. A stray seed got into the bunch, that's all. Like Laura said above... looks like a lemon cucumber.

There are yellow Lemon cucumbers and Dragon's Eggs which are white. Hard to tell exactly how they are growing but they should be perfectly good to eat unless you wait too long to pick. They had the wrong seed or crossed seed in the packet.

Looks like lemon cuke to me as well.

Or possibly, it's so unhealthy, the fruit is stunted and yellowed. What's the location? It's way too late and hot here in my area for cukes now.

How many plants are there? What is the source for the plant - seed or transplant? Purchased transplants can become mislabeled, and seeds can get mixed up as well.

FWIW, when you live where it's too hot for regular cukes, Armenian cukes are the way to go. I long ago swore off regular cukes for this reason. We're having 100+F weather now, and these guys love it. When you cut into them, they look like cucumbers, and they taste exactly like cucumbers too. But they're melons (Cucumis Melo), not regular cukes (Cucumis Sativus), which accounts for their heat tolerance)! Burpless as well.

How are Armenian cukes in re: root knot nematodes? They are a scourge here.

I've grown Armenian cucumbers before and we love them. I tried a few more of the yellow/white cucumbers and they're not bitter. Not lemon cucumbers which I've had before, but fresh tasting. Each of the 5 summers we've lived here in Southeast Coastal Georgia have been different weatherwise. Last summer the 100s didn't hit until early July so I thought the cucumbers might make it. Next year I'll try Armenians again.

I've never had any problems with root knot nematodes. Maybe someone with that problem can weigh in. Now, all cucurbits, in principle, can suffer from nematodes. So I'd have to assume that Armenians are not resistant.

Right now we are FLOODED with Armenian cukes. Giving them away, making baked breaded cucumber (yes, it's a real thing), cucumber soup, Tzatziki, cucumber yogurt salads, as well as regular salads and just sliced cuke plates.

What you need to know about them is that they grow EXPLOSIVELY. You see a cigar-sized one and say, eh, that'll be ready in a week. But BOOM, it's ready in two days.