Congratulations on your achievement. I'm sure that you have many more where that one came from. As far as you gaining an inch in height, you've always been 6 feet tall, but your "bad posture", so to speak, which includes weak neck, shoulder, and back muscles. Strengthen those up anyone will gain an inch or more. The same thing happens to me and I'm twice your age. I lay-off for about 3 months, height goes down to 5'11". I get back into the gym for 3 months, my height goes to 6' 1/2".
All due the muscloskeletal structure of the individual. Good luck on your next cycle.