Is that a Euphorbia tirucalli maybe? Called 'pencil cactus' sometimes. I'm not sure what is going on with it. Are both pics on the same plant at the same time? Is there a possibility that a branch has broken off the main stem, but is attached enough that it's still in place? I think it would be a lot easier to give this plant too much water than not enough, so if it's on a regular schedule with the other plants I think what I would do is give it less water and stop giving any fertilize at all. Maybe water some with plain water every other time or something like that. But I'd check for a breakage on that limb.
Maybe someone else will have some better/different ideas.
Donald
