Am I using too little nutes? Afraid of burning, but still having issues

[NorCAKnowYourGrow]

HELP!!!

Basic Facts:
Outdoor Grow
3 Sativas (Black Jack/Blue Dream) - Week 1/2 Flowering
3 Indicas (Platinum OG, Venom OG, Purple Punch) - WEEK 4/5 Flowering
1 CBD Dominant (Chocolate Tonic CBD)
7 gallon black Fabric Pots
12/12 light (black out in storage canopy at night)

Nutes: Humboldt's Secret
Base A: 4-0-2
Base B: 1-4-2
Golden Tree: 0-0-2
Flower Stacker: 0-7-5
Plant Enzymes

Issue: appears to be phosphorus def., but shows up as adequate in soil test

DETAILS:

I have been using Humboldt's Secret most of my grow. Up until a week or so ago things looked amazing. All of a sudden I'm getting what appears to be a phosphorus deficiency. I used a RapidTest soil test and it shows adequate phosphorus and slightly low potash. However, even with feeding my plants MORE Golden Tree and Flower Stacker I'm still getting yellow spots on my fan leaves.

I'm concerned with overfeeding and burning the poor girls but thinking that maybe I'm still giving too little nutrients. I have not seen any real signs of burn, however, just afraid I will burn them....

I traditionally mix up two gallons of nutrients as per the instructions. Then I divide evenly among the plants.

Is this just too little?

I tested my soil with the RapidTest and it appears my pH is 6-6.5. I keep wondering if this is right because I tested water runoff when I watered with 10-20% runoff and it looked like the pH was much more acidic according to the strip I used. Now I don't know what to believe about the pH - I am leaning towards the soil test with soaking the soil and then testing the water with the pH powder in the test tube.

This issue started about a week ago. It isn't rapid spread, thank God, but every day I find new affected leaves despite trying to give them more nutrients.

I've asked a few communities and am getting nowhere. I have worked my ass off with these plants - moving them three times a day to get as much sun as possible, putting them in a dark storage canopy at night. The last thing I want to do is lose them!!! The indicas are LOADED with bud.

i KNOW I have good nutes and I'm doing something wrong.

HELP!! PLEASE!!!

 

[NorCAKnowYourGrow]

Also....I had been feeding twice a week. Then I experienced rapid growth and massive budding. This past 7 days I've fed three times.

 

[Emilya Green]

yes, the picture of the damage does appear to be a mobile nutrient deficiency, but not phosphorus... I think it is potassium that you lack. Why is your plant short of this macro nutrient? I think because you are out in the bright sunlight and yet you are feeding like it was an indoor plant. Nutrient companies don't generally give their feeding recommendations for outside plants... so dont be afraid to up the nutrients to full dosage. A little bit of a burn if you actually manage to do out there is not a crisis either... I come from the old school who believed that if you were not burning the tips just a bit, you aren't trying hard enough. What you have going on is not tip burning though... you are not feeding strongly enough out there in that hot bright sunlight.
Then, pH. Soil is designed to have a base pH of 6.7-6.8... on the high side of the soil range of 6.2-6.8. It is designed to be this way so that when you water with a fluid adjusted to 6.3 pH, the pH of your container of soil will then range between that 6.3 - the base pH, depending on how dry that region of soil becomes. The top of the container where the soil has dried out will be 6.8 pH, while where it is still wet around the middle to bottom of the container, will be closer to the pH of the liquid you put in there. It is a beautiful system, but because of the merging of soil and hydro methodologies, there is some confusion about measuring the runoff pH and PPM in soil. In coco or a hydro type system, these measurements can tell you a lot about the liquid based medium you are using. In soil however, think of runoff as coffee out of a percolator. The more you dilute it, the weaker the coffee becomes. If you measure the pH of 5% runoff compared to 20% runoff, the pH and the PPMs of the two measurements will be radically different. Which one is correct? None of them... you can't learn anything meaningful from taking these measurements in soil... it just doesn't correlate to anything that is actually happening in the soil. Don't try to outthink the soil... just water each time, whether it is plain water or water mixed with nutes, after adjusting the final mix to 6.3 pH. Not 6.0... not 6.5... these are huge differences in pH. 6.3 pH every time, and your deficiency problems will go away.

 

[NorCAKnowYourGrow]

SOOOOOOO helpful!!

Thank you. Makes so much sense. I will up the nutes and not worry so much about burn.

Vegetables are so much easier than weed! I swear.....