I believe the most likely cause is that you created a calorie deficit which slowed down your immune system and the bodies ability to repair itself. Do not get caught up with these diets without proof you have a problem. I have made this mistake.
The red line you speak of may be an irritant effect to what you are putting on there, see my blog. Is this the same redness I am referring to ? I have seen improvement in this redness from using a different toothpaste which has no flavourings and only a fraction of the amount of ingredients found in most others.