purple stem and twisting, pleeeease help you guys!!!

so im 5 weeks in and prob bout 3 weeks left till harvest n a few fan leave stems on my short ryder are purple n twisted..
my ph is fine and rest of plant is good but want to nip in the but before gets a big problem..
heres pics and hope you can help me!
http://img19.imageshack.us/i/dscf1035e.jpg/
this is one of the stems but is more purple in person than photo!
http://img848.imageshack.us/i/dscf1033.jpg/
here you can see other stem purple n twisting
http://img820.imageshack.us/i/dscf1034k.jpg/
but flowers seem ok like in this one, in second week of flower

thanks guys

i have recently flushed as advised, could that cause purple stems