did darry change after he heard ponyboy was in the fire

Any time you see someone that you care about in a "devastating/devastated" situation, of course you change. In a situation, such as the one in the hospital, it seems reasonable to assume that Darry wants to express his honest emotion, which he has been unwilling to share before this. A hug is often something men and boys do not use to show emotion; it is considered uncool. Yet, when we realize we could lose someone, we change our attitudes about many things.