Your lead rushed the chord changes. instead of waiting for the G chord to come around, you came right in. As I said, absolutely everybody does this at first. The best cure is to count 1-2-3-4 with the beats. A lead player will simjply noodle around a bit until the change happens. Others, like the guy on my left during Sundays jam, changes whenever the mood strikes him. I could tell you heard the chord changes, you just rushed them a bit. Practice with a tape player helps, or better still, with live musicians. But as we can all see, this is hard ta arrange sometimes. Does this make any sense?