So, I finally made an upgrade from my old iPhone4 running the latest iOS7, which had a perfect screen color calibration, to an iPhone5s runing the latest iOS8.
And now I also have the warm-yellowish screen. I also noticed that colors are much more saturated and contrasted.
After installing the apps and getting all set up, I opened VSCO Cam and some of the photos looked A LOT more saturated than what shows up in my iP4. I made a print screen and, using the shared folder, opened it in the iP4 witch showed up just the way it should look.
I mean, this is clearly a calibration problem and how the phone is rendering colors... Now working with images and having to check them on the fly and editing my mobile photos with such a difference between what things are looking like and what they really are will become a problem.
The iPhone4 calibration matches pretty much my macbook display colors. Never had a problem in 4 years, even with prints. Now I better start thinking out of the box and rethink Apple.