Is this mag. def.of not??

[Muddy]

The purple/red in the stems can be caused by several things. It can be genetic or it can be from a lack of P caused either by not having enough, it being locked out or by cold temperatures. Some strains, Mi5 for instance, often needs additional P during flowering. I always keep a bottle of PK13.14 on hand just for such cases. You're a bit high on your pH. 6.2 - 6.4 is optimum.

 

[lazylathe]

From the look of the leaves it is over watered.
Wait until the top 2 inches of soil is dry before watering again.

The purple stripes could be genetics or also from the nutes or lights you are using.
Mine started to develop purple stripes when i added my CMH to the mix.
Looks pretty cool to me!