Sunburn Or Worse?!

[MSPProductions]

I have to say first that this guy never seems too happy and I recently moved him to a little brighter area. It did give a bit of a groth spurt and then...
this leave on the oldest of the new growths started to go pretty rapidly.

It's a complex Paph. that bloomed about 7 months ago and is potted in coir, watered once a week, with an extra watering if things look too dry. Very weakly fertilized 2-3 times a month.

Is this just sunburn or am I looking at something worse?

[Sharyn]

Not sure if that's sunburn or fertilizer burn. I just burned up some cattleya leaves with sun and the huge spots on the leaves turned very black. They really look french fried!

[kmarch]

It looks like some type of bacterial rot to me. I would immediately cut the dying part of the leaf off and treat with a fungicide or anti-bacterial. Exhibition Paphs, while not able to stand very bright light can tolerate higher light levels than many other Paphs so from your post It does not sound like sunburn to me. If it were fert. burn, only the tips of older leaves would be affected.

[Tobi]

It looks like black rot fungus. This starts with soft purplish brown
areas that will eventually turn black. At times you can see yellowish
margins around the infected site. Remove the infected area with sterilized
tools or razor blade and treat with a fungicide containing etridiazole.
Keep the plant in a low humidity area and water carefully. You can repot
once the plant recovers. Good Luck!!

[MSPProductions]

kmarch and Tobi, thanks I will take your advice and get rid of the infected leaf. BTW kmarch, I think I read that you are a fellow composer!