hey bro.. i lost the subscription to your journal somehow.. i missed a lot!! damn your girls are looking good... finger lickin good
so as far as the purplin goes, i really think its natural... you can tell if its not by 2 things.. 1, are your buds slowing in growth?? if they are then it could be a def.. or the other way is to give them a little extra shot of bloom nutes and see if the purp tones down a little.. but i really really doubt you have a def... it looks like an heavy purple strain would look at about 1/2 way point of the grow... give or take...
the other thing you may want to check is your soil PH.. if the soil has a ph of 7 or better then phosphorous becomes unable to be absorbed right.. if its to low then the the soil can become chemically bound to the phosphates.. either way would show a deficiency.. so if you eliminate the 3 things that would show a def, then you will know its just natural... and really non of the ways are in any way hard... but i will say it again.. it looks fine and normal to me...