Have a clone of the Tangilope I’m currently flowering, and despite nearly identical feeding routine, schedule, and pH as last time I vegged it out, a deficiency has arisen, oh no!
Still feeding with GO box, adjusting pH with “PH Up” – potassium carbonate – so potassium is the last thing I’d expect to be lacking. But, that does look like potassium deficiency… right? If so, I’m up for recommendations on what to do 
I think you are on the right track. Potassium Sulfate Might be in one of your amendments. It is water soluble and supplies sulfur which is good in flower. You could add a little extra. I like potassium silicate also but it is slower and better to use less more often which is why i like to use it to raise ph when i feed or to add ppm when i use RO water.
If youre using the go box to a tee you wont have defs. I never had to ph anything and never had any problem. What is the ph of your food, plain water, and runoff? Also how often you feeding? How far into flowering? Ive seen many kinds of stress do crazy things to plants. Where are fans pointing? Any direct wind on these leaves at all?
pH of full-strength GO nutrients in my water going in is about 4.7, which is rather brutal. That’s with Grow, BioRoot, BioMarine, BioWeed, CaMg+. I did try swapping out CaMg+ for epsom salt for a couple of feedings, didn’t notice much of a change.
pH of my tap water is 9.5 – mind you, that’s intentionally raised by the city with… something. Mineral content, I believe, is quite low. Run it through a carbon filter to try and reduce chloramine, and add a pinch of EWC for good measure. I adjust to ~6.8 when giving the girls a drink.
Run-off seems to add a dash of acidity: testing tonight, I adjusted nutrient solution to 6.6, and run-off was around 6.3.
Feeding… often 
I’ve been giving these two 80% strength every 3-4 days, plain water maybe every 4th watering.
Not currently in flower, at least another few weeks until I have space in there.
Fan leaves are basically flat, horizontal. No direct wind, just a gentle fluttering from the 2 clip fans I have above the canopy for circulation.
It might be worth while to go with RO water. Your tap water scares me.
Yes you shouldnt use that water at all. Go buy 5 gal jugs and fill em for like 2 bucks each. Thats what i have to doXD
… yeah, it scares me a bit, too, but I thought that was just because of my preference for sativas 
I have some jugs of distilled water and spring water… guess I can try a couple weeks of using those instead of my tap water to see what happens.
YES youll notice an amazing difference paying for your water. Most of my water goes into my humidifierXD
I was actually using jugs of water when I was re-starting, and literally had 3 beans to my name. In the abject terror, I was basically wearing a clean suit, giving them individual drops of water analyzed under a microscope for impurities.
Oh also, as a resident of an urban area, my water runs were done by bike. Pop by the store, buy 6 gallons of water like a crazy person, and ride home with an overflowing basket in the middle of winter 
Anyway, will probably go the RO route – that’s what I had as a wee youngster grower, and I learned to handle the constant Mg deficiency. Strangely, Ca was never a problem!
i belive its to much potasissum
Out of curiosity how are your roots are they fully developed or a little on the thin side?
I’ll tell you when I repot, which should be within a few days.
Sprin water is hi ph I would just go an get a ro buddy there not that expensive an will save u boat loads in the end best thing I ever got
May be easier to diagnose with a full plant pic. Are the leaves from the top of the plant, middle or bottom?
If the top of the plant is good and green I would say your issue is Nitrogen.
I would also agree you shouldn’t need to PH even with a PH of 4.7 as I am 4.9 on the regular with zero issue.
Yellowing on new growth (top)indicates to me it’s an immobile nutrient. Imobile nutrients can’t translocate from my understanding of it and won’t move down to the lower leaves. So we’re talking about anything other than N,P,K, mag and zinc. Since your haveing an issues with wide swings in Ph with starting water and going in nutes makes me believe it a ph thing first and foremost, Ph can lock out nutrients both with low and high values which could look like a deficiency when in fact you may not have one to begin with. Get your Ph squared away first with good water that’s reliable and go from there, hope this helps!
How’d this old thing get bumped? 
The plant this came from is about to finish flowering. It had plenty of other problems after this 
Anyway, leaves were lower fan leaves – only old growth was impacted.
I did end up getting an RO filter in response to this thread, seems to get the job done. Have had a multitude of other problems since then, particularly in veg – my current suspicion is slow-but-steady overwatering, probably leading to soil pH issues and weak root system – I’ll update this thread with progress soon.
