1st time grower problem

Northern Lights started in solo cups and repotted twice to larger pots. Using Fox Farms Ocean Forest. Indoors under 150w HPS. I don't have space nor the need for some huge plant so I vegged for 3 1/2 weeks under 18/6 and have been flowering for 2 weeks 12/12. I also have a Blue Mystic. I have watered with tap water that I let sit out for a couple of days and ph'd as best I could to 6.5 - 7. I don't trust the meter I have so I also check the ph with one of those tube and drop solution kits. I have given them one dose of nutes (Botanicare Pure Blend) shortly after I started flowering. These spots have been showing up on my NL. Not sure what to make of it. It has been the most vigorous plant. Don't see the issue on the Blue M.

Ffof is hot!......if recently repotted, just give plain dechlorinated water and no nutes.....what are you using for ph adjustment in this organic soil?

I haven't used anything. Should I? The product claimed to be ph adjusted to, as I recall, a number suitable for weed. I have read that it's potent soil but I've also read numerous posts here and on other forums of folks having success with it. I mixed it with about 33% perlite so it's pretty airy, if that makes any difference. I check the ph of the runoff and early on I was concerned as it seemed quite acidic but the last check I did it was about the same coming out as going in. Other than those spots it's been a healthy and vigorous plant.

Didn't you say you gave them a dose of pure blend^^?? Full dosage?

Personally the girls do look good overall and your mix is fine, would just continue to use nothing until fading (yellowing) starts or defs occur.....ffof has about a month worth of organic fert in it until feeding should start......generally

Good luck grower and keep it green

I was confused about your question, "what are you using for ph adjustment"? I was using a ph down solution that I purchased at a hydro store. And I didn't need but a drop or two, if that. I fill a 5 gal. bucket and let it sit outside for a couple of days. The ph seems about right without doing anything. When I first started I was using store bought water but as they grew that got to be a pain.

I really read and researched a lot before I attempted this. One thing i seem to keep reading is not to go do something stupid. Ive just watered them when the pots seemed really light and dry. I only gave them a dose of nutes when they started flowering. It was suggested on the FF's website. I suppose it was generic instructions for flowering plants. And no I was carefull and didn't use a full dosage. The brown spots had started before the nutes

Actually I'm somewhat astounded that I've made it this far.

Looks like you need to flush your medium and then feed at 1/2 strength. The NL strain probably isn't as nute tolerant as the BM and its starting to burn a little.

Yeah, definitely just the first sign of some nute burn, but not bad. You should be able to recover fine with a good pH flush (or how ever many it takes) and next time you feed just slowly work your way up.