Random holes in leaves and yellow spots *NO BUGS*

growing in 50/50 coco/perlite using a 600w MH
I am using fairly hard tap water (270ppm)
temps are 70 at night and 75 in day

any help would be much appreciated! everything i do hasn't seemed to clear it up yet!

Put out some sticky traps to inspect for type of bugs.

Thanks for the replies guys, i already have 2 yellow sticky traps out that have been there for about 3 weeks and not 1 thing on either, really have inspected closely for bugs and there is nothing, the PPM of my feed is around 570, 300ppm of nutrients added onto tap water ppm, ive just given one of them an extra feed today to see how it responds, problem seems to have got worse over the last 24 hours, any help appreciated!