That does sound as though it's discolored from someone's head resting there. Or perhaps a pet makes that a curl up spot? A picture would help diagnose it better.

I have never seen my small dog lie on the couch and usually no one sits in this spot unless we have company.
Just not sure.

Roof leak? Plant watering accident? Is it still under warranty or an extended warranty?

The plant behind is plastic and had a warranty for 5 years and it is 7 years old. Ceiling is just fine. Just odd that this happened. It is a lazy boy couch.

It looks like someone washed something off of it once.

It does look like someone cleaned it with a "not for leather" liquid.. I've never seen discoloration like that and in such a specific location. If you have a leather shop around, can you take the cushion to them for some idea regarding refurbishing?

"The plant behind is plastic"

Do you EVER spray anything on the plant to clean it?

Like spray and then wipe the plant clean of dust.

Thank you for all your postings. Never has this couch been sprayed even my plastic plant I clean in the sink. I have only used lotion that is to be used on leather couches and no other place has this problem on the couch.
I am getting a professional leather restoration advice and will come to the home.
Thank you and I am anxious to hear what he feels is the problem!

"even my plastic plant I clean in the sink."

Is it perfectly and completely dry before returning to its location?

As in allowed to sit overnight somewhere else?

How did you get on about your couch discolouration? I'm having a problem with my white couch turning pink and can't work out why.

Sorry I cannot be of help. I have no idea what happened and so I had an extra cushion due to a mistake in the order, and got someone to use that leather to replace the darkened leather. The leather fellow had absolutely no idea what had happened. I truly believe it was in the leather.