Flies??

I have 3 plants that are 2 full weeks into flowering. So far everything has been fine... till day 15. When I checked on them they had flies all over them. Like 12 or 15 flies. I'm so new to growing that I have no clue what to do. Is this a normal thing? Has anyone else had this problem? Is it even a problem? I'm growing inside my shed in a 2ft. by 4ft space.Do I need an insecticide and if yes what kind? If I spray the plants, what about bud-rot? Can anyone give me some advise?

You need to seal off the shed so more flies can't get in(but not at the expense of circulation), but you should start with hanging some fly paper, plus they're not that hard to swat. The little buggers are attracted by the smell. Kill 'em all.