Not really. Phosphine is broken down by UV light so having it be concentrated higher in the atmosphere, where it's exposed to more UV light, would be difficult to explain via transport from a lower altitude source.

Not if it gets produced and transported (slightly) faster than it's broken down.

This is a possibility but we’ll have to see what the paper makes of this, if anything. It may depend on knowing more about the motion of the atmosphere. It was also an unexpectedly large amount of phosphine apparently, more than would normally be stable at that altitude (so it’s definitely being renewed).

But again, this is just a string of tweets—hard to say anything without the paper!

Yeah, "wind" seems like it could explain much here.