This seems to me to be more of a soil type grow and ppm concerns are geared more toward hydro with a reclaiming feeding system, although I can see some pertinenance being you are just using rockwool. Now in my opinion, not that the nutrients you are using are bad, which they are not, but I would get some fertilizers that are formulated more toward hand feeding and if your are going to hand feed I would recommend using a good organic soil with bone meal and earthworm castings in stead of the rockwool.

It does look like some of the tips are burning a little bit to me but it also looks like your plant wants more root space. How many plants are under that 1000w?
JeffersonStateGrower Reviewed by JeffersonStateGrower on . more nutes or less with blue widow im using 6 x6 rockwool cubes. hand watering drain to waste. 1000w hps in doors. 18 days into flowering. Gh flora. at 1 micro to 2 bloom ratio no grow. 1/4 tea per gallon of powder koolbloom. mixed to 1000 ppm at the present time. do these plants need more ppm or less? more nutes? are they getting burnt? any help much appreciated. im asking because gh's nute calculater says that you should not go over 850ppm. i did that for the first few weeks and just a few days ago went to 1000ppm when i saw Rating: 5