question about adding more light for flowering?!?!

hi! here my setup...then my question...

4 auto flowering plant
Grow tent just perfect fit...
dimmable ballast (250-400-600W) i use 250 to start then i go up to 400...and i use HPS bulb only...
temperature day:24-27C depend on the system changement(its all electronic) night drop to 19-23C
good aeration..air from outside go in the tent..carbon filter...

neutral soil...
tap water sit in bucket 48hours

nutriment:
BIOCANNA flores (im in flowering now)
MAGiCal(magn,iron,calcium)

and the highest plant its 9 inch from the light ...smaller around 13 from light..400W

i wonder if i should put the light to 600W to give more light...cause i read a lot this :
more light, more buds... but i know auto flower get easily stressed so i dont want to hurt their feeling

Thanks

what size is your tent? as long as you keep your temps in check and you don't let them get too close to the light you will be fine

32 inch by 32 inch ...tall enough...if i do that i shoul put the light up a little too maybe? or it will stretch the plant !?

autos love light the more the better. autos grow like weeds.
feed them good and light em up like a phatty???