same strain, same room, but buds are pink on some, not all

Hey, i got a room 4x4x7, 8 girls, 1000W hps, 12/12 cycle, 4.5 weeks in so far, Hydro setup. i got the same strain of weed, but the hairs on the heads on the plants at the back of the gullys have turned pinkish where as the buds near the start of the gullys is just white, the humidity is a little high and im working on getting that down atm, what could cause the hairs to go pink on the buds at the end of the trays?

my mate reckons its cause most of the nutes are getting asorbed first by the plants at the back (the pipe go's into the tray at the back) thats why thereve turned pinkish, but i think it may have something to do with the humidity, what could be causing this?

btw all the plants are definatly the same strain, no doubt about that.

some pics of the girls from about a week ago:

phenotype is the word your looking for

phenotype? nah like is it humidity, or is my mates assumption on the right track or what?

pheno type means a plant of the same strain that can look and smell different! you should prob try get some clones off it you could have a keeper there!

oh wow nice!, yeah well the clones were from all the same mother plant, interesting

i saw a strain not to long ago called 'The Forbidden Fruit' and it has hues of pink, blue, orange and red... looked like some crazy buds.. anyone seen it or grown it? looks phenomenol!

so if i took a clone from those pink girls and turned that into a motherplant, would the cuttings from it bud into pink buds from then on? is this like some stage where the strain evolves or something?

Actually, phenotype is not what im looking for here, Im wondering why half the same strain has got pink hairs, while the other girls from the same mother have diff coloured hairs, phenotype means sativa/indica/hyrbid mongrels or w.e, from what ive read here anyway. So would my mates conclusion make sense about the nute thing?

still need help with this one

here I'll simple it for you...

Your bud sites are becoming pink, Sounds like a phenotype but you cut the clones from the same mother... So that is weird but it is still possible that it is a just a pheno trait causing those pink sites...

If you believe its the Nut causing the pink buds then an easy way to test it is check the roots are they also dyed pink?

Here is a list of minerals which give of the pink hue and cross check your nut maybe it contains to much of any of these given minerals.
http://webmineral.com/determin/pink_minerals.shtml