Need advice

I am including pics, I am new at this indoor stuff. the top of the plants are getting yellow. the lights are 400w cfl there is a multi and 2 flower bulbs in it now, I had 1 multi spec and 2 vegetative bulbs until xmas then I went to 12/12 lights and cut the nutrients back as indicated on bottle. I have lots of questions of cource but the yellowing is my biggest one.
other questions are with regards to pruning I was told when the sucker leave produces a new growth and its 1" cut the sucker???

How do you keep plants short and fat? I see some like this..is this good?

Thanks for the help

I think u got urself some nute burn there man, although I'm not an expert on the subject - next time u switch out ur water go half strength on the nutes, and start doing this every once in awhile, i think its every other week, hopefully someone will answer the time gaps on that
other than that, you should add a fan in the room to strengthen her up, the stems are lookin a bit weak for how big it is, and won't be able to hold the weight of buds unless u work em out

as far as keepin em short n fat, theres lots of ways -the one im about to use on my upcoming grow (seeds in the mail) is a technique to get four colas https://www.rollitup.org/advanced-marijuana-cultivation/151706-uncle-bens-topping-technique-get.html -or any other topping techniques generally build the plant more outward than up
also check out LST; and the main way when growing with CFLs is just light placement, the plant will slow down vertical growth if its too close to the light, and stretch if too far - adjust as needed

hope this helps, good luck