Any thoughts would be great leaves turning yellow and getting brown spots and tips

leaves are turning yellow and getting brown spots & tips of leaves are turning yellow, nut changed once a week...could this be a low nut problem or over nutrients?

• The following nutrients were added per gall x3 = 3 gall.
  Aquaflakes A & B: 3 ml
  Nitroboost 0.3 ml
  Multizen 2.5 ml
  liquid karma 4 ml
  Root excelerator 0.3 ml​
  
  
  
  

Here is a good photo reference:
http://www.growweedeasy.com/marijuana-symptoms-pictures

What is your ph level? What ppm is your water? I have done dwc before and I didn't put anything in the water for the first 2 week.

thanks for the quick reply!
ph is 5.5, how can i check the ppm? i have a hydroponic store near by that i can go to.
On another forum i was told that this could be a CaMg issue? what do you guys think? Ive been using nutrients from the start, should i try to lower the nutrients? Im affraid it might lead to nut lock