Skinny Stalks

I have posted before about my plants being tall and skinny,but i had the light to far away fron plants.I now have my 400 watt hps light about 10 inches from my plants but they still seem to be tall and lanky for some reason.It's only 2 out of the 5 thats doing this & i even swiched the buckets around from the light,so has anyone got any ideas why the stalks seem so small on the tall ones?They still look healty tho so i might just let them grow & see what happens,and i got the fan on them blowing on low so i don't think it's to much air.Any info be appreciated.

Um do you have a fan osolating on them?

It might just be just the strain

Yes i have a 16 in rotating fan on them thats on low for now,and i have the BIG BUDDA CHEESE strain that i'm gowing.My outside grow this year was awesome i had some plants that was 10 to 12 foot high.I'm sill wondering tho if i should prun out some of the tops like i did outside or just top it alitle so i'll have a less busher plants!I think they'll be ok form the way they look,it's just that i'd like to see the stalks get alitle size on them.The shorter ones look good there stalks got more size to them.Do you think i have the light at the right height?I got it about 10 to 12 inches from the plants and it doesnt feel that hot ,so i guess i'll just keep my eye on them & see how they go lol.Thx for the info.