What to do if plants stretch too much?

It's almost the end of the 3rd week of flowering and my Pink Kush plants have stretched SOOOO much that they have stretched to and above the light. The first pic is at about 4 days after I flipped the lights and the other pic is today (almost 3 weeks).

What were about 12" tall when I flipped the lights are over 36" tall now, I anticipated that they would double ... but not triple.

Does anyone have any suggestions on what can be done? Is it acceptable to top the ones that are just too tall? I really .. really don't want to do that but these girls don't seem to be leaving me much choice.

It's an air-cooled hps reflector (600W dimmed to 400W) in a 2'x4'5' grow tent (only 5' height to work with). There is no scrog net, a member of this forum convinced me against it this grow unfortunately or this probably wouldn't have happened.

Bend them over.

Just had to bend for the same reason, they went from 8" to 28" in 9 days. I bent the tallest ones and they didn't even seem to notice.

Super crop (bend them over)

OK i'll try supercropping, never done that technique before let's see how they fare.

Edit: I cracked one so I decided to top it, we'll call it an experiment. Sad to see these huge tops bent over like a limp dick though.