It's impossible to tell whether a horse has grown taller just from pictures unless there is the same person or tree or fence beside them in both pictures...at the exact same angle and in the exact same place.
Though the second picture isn't such great quality, it does appear that he's put some weight on. That can make a horse appear to be taller when you handle them. I went through that last fall with my 4 year old. I went out in the pasture and just knew that he'd grown another 2-3 inches. I brought him in to the barn and put a stick
to him. He hadn't gotten any taller, but he had really bulked up and gotten much bigger in every other way.