problems?

These plants are grown in soil, I use Reverse osmisis water, foxfarm nutrients, i test the soils PH weekly and It maintains around 6.3 to 6.5 these plants are vegitating my light is a 600 watt HPS conversion bulb, this is my third harvest and this is the first time this has happened, I have been watching carfully for incects and have had a few gnats but that is it I have flushed twice and it seems to be spreading to other plants, should I just abort these plants and start from scratch I am at a lose, if any one has ever seen, or has any ideas they would be much appreciated. thank you

Also the the rooms air is completly replaced with fresh air every 2 hours

RO removes all Magnesium & Calcium that FF nutrients don't replace. If you are using RO water religiously then I would ensure you invest in a bottle of CAL-MAG Plus and dump enough of it in your water to start at 100PPM's. This will help serve as a buffer for your waters PH & get back the micronutrients that your water & plants are missing.