sticky stain or bleaching on leather couch

Greetings
We have 2 separate problems on leather couches.
The leather is fairly thin medium-to-dark brown.
In one place, there is a spot where it has gone yellow. And it feels sticky. My wife, the pretty-much-everything maven, cannot get this cleaned up. It looks like a bleached patch to me. Can't get the stickiness off it, and dyes don't take on it. (Roughly 3 in. X 1 in.)
Unclear whether it is something still adhering or something bleached out or some inner chemical property of the leather.

Problem two is on another couch, same leather, where there is what so far is an indelible dark stain.

If pix or details I can't think of will help, we'll provide them as possible.

Thanks for being here to ask!

denno

Without photos, its difficult to make any kind of recommendation. These sound like they are both beyond what you can fix as a consumer, however. What I would suggest is you reach out to Pam at Leather Solutions International in Asheville NC, and make arrangements to remove the seat foam and send her the casing. She can restore it better than anyone on the East Coast in about a week's time. Do one at a time or send her both. Pam is known in the trade as the "Go To" company for this sort of thing among all the major manufactuers.

https://www.facebook.com/LeatherSolutions/