I am so sorry that you lost Tortilla. The left eye on Cola could possibly be ocular Mareks disease. Is the right eye changing color or is the pupil less sharp in appearance. Here is some reading about Mareks just to help in case that is what is happening in your flock:
http://csu-cvmbs.colostate.edu/Documents/vdl-mareks-disease-fact-sheet.pdf
https://www.backyardchickens.com/articles/the-great-big-giant-mareks-disease-faq.66077/
http://csu-cvmbs.colostate.edu/Documents/vdl-mareks-disease-fact-sheet.pdf
https://www.backyardchickens.com/articles/the-great-big-giant-mareks-disease-faq.66077/