Is the Durban Poison doing alright? The leaves are...

I think it will be fine. Especially when the plants are young like that they can be impacted differently by relatively small stuff. I'd check to ensure that whatever you're watering with is pH'd properly to make sure nothing is getting locked out. If everything is looking solid with your pH it's likely just some growing pains for the Durban. I'd expect that it grows out of it within a week or so and stabilizes.