I have this exact same colony. Ironically I have watched it lately and it reacts to everything. This type of polyp is well known for crowning, also called an umbrella like appearance as it tucks its skirts underneath the oral disc and puffs upwards. It will swell, thin out and the disc itself will even swell in high current and bright light. In my opinion, there is absolutely nothing wrong with it and nothing to worry about as this particular polyp does lots of crazy things and it is perfectly normal.
Mucho Reef