Nutrient burn or Deficiency

I have all four plants with yellow tip leaves my EC was 1.8 but reduced it to 1.4 the plants are 4 weeks into veg and topped in bubbler buckets ph is stable at 5.8. I was thinking its nute burn but not sure could be a deficiency? http://youtu.be/LnzS8pvIFLA

It's a zinc deficiency........which is usually caused from your pH being too high. Foliar feed using chelated zinc.

I always run a slightly higher PH when in DWC than in a flood n drain.

Take a look at the chart for different nute uptake at diff. ph levels and see what falls in the range of where your ph was. That will give you a good starting point

thanks people for your advise