looks like nute burn to me, i didnt start nutes till late in my 2nd week and even that was 1/8 or 1/10 strength. what kind of soil are you using, alot have fertilizers already in them and any more will almost always burn your babies
As Mys said, plz post the soil and also what kind of fertilizer your 20-20-20 stuff is (and any other ferts you use). It sure looks like nutrient burn, in which case flushing would be the next step.