various strains grow issues

i have been growing 9 plants (3blue cheese 1cheese 1silver cheese 1special k 1bubblegum 1 wonderwoman and 1master kush all under a 600w hps light in soil in a tent i made, after 39days veg most plants were 12inch(bar2) my master had stretched slightly more than the rest but also at the time i 4t i had nut burn as some leaves were yellowing with brown spots so i flshed it but seems its not the case??? think it could be to close to the light ??? 50cm was the hight directly under most plants and they are fine but mk's top kola has burnt badly so 2wk into flower i decided to trim it off should i have? plant still looks ill.
also has anyone tried growing the silver cheese as its the only one that still doesnt show its sex yet 2wk 3days into 12/12
mant thanks for any help will try post pics once got a cam and usb

well its like they say ...... want a job doin then do it urself pmsl just incase anyone is interested the answer to my original q is yes its ok to trim it as needs must and master kush is still goin strong with bud sites poppin up all over now, ok its more of a pale green compaired to the rest of my girls but still doin well
and as for the silver chees q then my answer wud have to be that because of the fact its crossed with haze means it can take upto 4 wks longer than most cheese strains to finnish hense the lack of comformation that it was female but i can now rest easy as after much research of my own i feel safe in the knowledge that its NOT male.
ok the fact that im a noob to the art of growing might not of got me any answers with the way i word my thread but heyho im more positive than some of the lazy noobs who just constantly ask q's and dont bother researching for themselfs

I'm growing MK for the first time (hydro) and have come to find out it is a very hearty plant. they dont seem to like nutes as strong as the Medi-bud I was growing, in fact I has to cut the mix by 1/3 as to avoid burning the plant. You can trim the heck out of it and she springs right back. I just started week 3 of flower and also have healthy plants with MANY flowers popping all over the place. :weedpoke: