with cfl you want them as close as possible with out them thouching the plants if they are cool white,however with warm white they have to be kept at least 2 inches away.I'm suprised you have a heat problem seeing as they are 6 inches away,do you have any ventilation in there?or a fan blowing on them?and you want to replace those soft white bulbs which put out more red light and alot of heat, with daylight or cool white for vegging.Or just keep the day light ones that you have and put them with your 400w hps,this will be fine for vegging