how do you know you arent overnuting them? what are the numbers for your NPK? are your leaves showing any stress too? It might not even be a problem with your plant, the lower hairs(pistols) are the ones to first mature on the plant, they should go from clear, to milky white color, and eventually turn amber/orange/red depending on strain. However three weeks into flower is a little early for all of that so I'm not sure, some pictures would be the only way anybody could help unless you be more specific of whats wrong with these burning hairs.

also do you have a thermometer/hygrometer in your growroom? If so what are your temps and humidity at?

Im growing White Widow and i got 25 celsius and huminity 65. My vent system is ok u can see it from my grow setup pics in gallery. Well i have been using 50% less Hesi Hydro Bloom (green) with EC NPK and 100% correctly Hesi PK 13 / 14 extra phosphorus and potassium (blue) and i have using it for

Week 1 - 25ml/10L water
Week 2 - 50ml/10L water
Week 3 - 7.5ml/10L water
Now going for Week 4 and i used 15ml/10L water.

As it says in the bottle.

can it be over nuted?

Well i have to say it cause noone else has, pollinated hairs turn color like overnight, any chance you missed a male or a hermi somwhere? 3 weeks sounds about right for a male busting a nut on your girls.

Hope not
P@ssw0rd

fuckkkk i think i fucked up!

it says 4week,5week,6week,7week and 8 week with water only... ffs so i needed to start using blue hesi at week 4 of flowering? and greenhesi for 1,2,3,4 weeks?

I didn't even think about it being pollinated, but I guess that would be another reason for hairs changing all of the sudden. You should do a check up just to make sure you dont have any hermie's on your hands.
As for bluehesi and greenhesi I am not familiar with either product, I am hooked on Cutting Edge now, it works magic. But from what you said it says on the instructions you might have given them too much P too fast. The numbers 13/14 are a pretty high numbers in my opinion, expecially for a plant that is just going into flower, do you know if greenhesi and bluehesi are made specifically for cannabis? Anyways if you did read the instructions wrong don't freak out. I would suggest giving them a good flush, and then restarting back on week 4 with what it suggests for week 4. hope that helps a little!

Im pretty sure it has not been pollinated... i killed all males very early. But overfeed, maybe indeed. i need give them water for 1 week now and start it all again. thanks for all the reply's mates!