Leaves turning purple??

[sonomacoma]

im on day 27 of 12/12 i currently have 4 plants from clones all of the plants were doing great untill yesterday i noticed 1 of the plants leaves started turning purple not every leaf but maybe 10-15 leaves on the whole plant i have herd of nitrogen defecency or potash deficency could do this ive also herd cold weather can also do this the room stays in the low to mid 70's during the daylight period and gets pretty cold in the night time due to my intake system pumping in cold nighttime air any info would be good is this somthing to worry about? here is pics not the best quality

[sonomacoma]

forgot to mention during veg i used foxfarm grow big and now im using foxfarm big bloom

[Abattoir Dream]

check temps at nite, 55-50 faranheit will turn leaves purple, cant see in that pic tho, put it into whiter light... and take a pic of it then...

some strains change colours through flowering, ive seen nyc diesel with pitch black leaves...

usually when its a temperature problem, the veins will go purple before the whole leaf...

good luck...

[sonomacoma]

so do you think if it was from low temps it would take anything away from growing up to its full potential