What is going on with this phal's leaf?

[Brownthumb10]

See attached picture. The other leaves look fine. I noticed it a few weeks ago (maybe 2). Hasn't gotten better or worse. Should I be concerned? Thanks!

[Bill U.]

That looks like that could be some sort of mechanical damage or potentially an isolated spot of sunburn? It's a little bit difficult to tell from the picture. However, if it is not doing anything, I wouldn't really worry about it right now. Just to be sure that it isn't getting bigger, I always make a small mark with a black Sharpie to serve as an indicator. A tiny little line won't hurt the plant or the rest of the leaf.

[lepetitmartien]

Bill has a clue.

But I'd suspect spidermites too. Check if they are still at work.

If something like little zones of necrosis appear, there's an associated fungus.