I see you do not mention your medical oncologist or a problem from chemo, except unable to have the 3rd Cisplatin. Chemo has just about the same side effects as radiation, plus it can damage the mucosal lining in the mouth, esphogus, stomach, bowel, and interfere with the digestion, and elimination process, and getting adequate nutrition, in addition to others. Most my problems initially, even still, are chemo related, and were worse than radiation to some extent, and am still recovering some effects almost 5 years later.
Maybe see about getting a full blood work-up. Certain deficiencies can alter taste, and appetite, besides being damaging, and see a Nutrionist who can delve deeper into your diet and eating habits. Although yours sounds healthy and well balanced, posture, eating speed, food combinations, in what order, et. can have an effect, and smaller, more frequent meals like 6, and adequate hydration from liquids and food may help. Drinking water 20 minutes before eating may help digestion, limit water with meal if that can be helped, but I need water to help swallow, just to name a few.
Good luck, but like you said, otherwise everything seems great. Congratulations!