Lighting Ud

I was in an office a couple of weeks ago which was lit by  those 4 tube flu light units  i think was 4 x 2 foot tubes but not sure also in the middle of the ceiling was a LED lamp one of those large square ones anyhow I noticed that around twice a minute the light would flicker momentarily  then after that have a noticeable 50 or 100 cycle flicker which would quickly go away only to be repeated a short while later. I'm not sure if this is a supply issue or just a cheap crappy lighting unit  i find it difficult to believe it's the supply as the office is right next to the substation. Either way if volt drop is the issue it needs some careful thought if they eventually replace all the flu lamps with LED 

I was in an office a couple of weeks ago which was lit by  those 4 tube flu light units  i think was 4 x 2 foot tubes but not sure also in the middle of the ceiling was a LED lamp one of those large square ones anyhow I noticed that around twice a minute the light would flicker momentarily  then after that have a noticeable 50 or 100 cycle flicker which would quickly go away only to be repeated a short while later. I'm not sure if this is a supply issue or just a cheap crappy lighting unit  i find it difficult to believe it's the supply as the office is right next to the substation. Either way if volt drop is the issue it needs some careful thought if they eventually replace all the flu lamps with LED