Are there a lot of leaves like that, or just a few? Is it a fairly young leaf, or an older one from near the base of the plant? A photo of the whole plant, or a bigger section it, would be helpful....

That leaf was the worst one. There are a couple getting yellowish. This leaf was not the oldest but was certainly not a young one.

Here are some more pics

It is putting on some new growth

I think it's probable that was simply an old leaf that had come to the end of its natural life...older leaves near the base of the plant will yellow and eventually fall off and that's perfectly normal; the plant looks very healthy to me and the presence of new growth is a sign that most likely all is well...unless the condition spreads or gets worse I wouldn't worry too much about it....hopefully others will come in with an opinion...

Monica, I have had my huge Pub PS for 8 years. Almost at every single watering, I loose a few what I call 'banana' leaves (ones that turn yellow). Sometimes they are large and old, sometimes they are smaller and young. This happens to me at every watering. I had just watered it 2 days ago and found these in the foliage this morning. Only with Pubs have I seen this happen with regularity. Here are this mornings offerings I found underneath the window.

I don't know why this does what it does, it doesn't matter if I give it a sip or a drench. As you can see, the new growth keeps on going so I believe that they (the yellowed ones) have just outlived their usefulness to the plant as shelley stated above.

Marco

Thanks. I feel much better knowing it's common (maybe especially with Pubicalyx varieties) and that I'm not killing it.