See that's the funny part -- she hasn't been getting any nutes since day 1. No miracle grow BS, strange nute-infused soil (just dug up from the woods & sterilized), nothin. I gave her 1/10 dilution urine 2 to 3 times total, but not within 4 days of topping her. It did that all by itself the day after the event.

The only thing I can think of is that I recently discovered it's been getting sprinkler water every night (had no clue til I checked on em last night). I think, then, that it might be a pH issue since tap water over here is about 7.4 pH. I don't see how it could possibly be over-nuting, and it's not like it's browning around the edges or getting discolored/yellow at all. The brown hasn't spread either since yesterday.

Could it possibly be too high a pH, mixed with chlorine and/or other metal overdose due to sprinkler water every night?

Oh, and the, uh, mandatory form:

What is your experience level? 2nd grow

Your Equipment:
.1) Type and wattage of lights. sunlight
.2) Distance from tops? the sun's distance
.3) Reflector type? none
.4) Is there a consistent fresh air supply? Yes, it's outdoors
.5) Do you have an exhaust fan and a circulation fan? The wind
.6) What are the bulb wattages, kelvin ratings, and schedule? The sun's cycle

Your medium:
.7) Specific brand and type of soil: Dug from the woods near my home, nothing added
.8) Size of container. 3 gallon
.9) Did you use peat pucks (or similar) to root clones or germinate seedlings? No, germinated the plant in a moist paper towel

Your nutrients and water:
10) Source of water? What's it's ph before adjusting? Filtered tap, and sprinkler. Haven't measured pH but tap water is 7.4 and filtered prolly ~6.8
11) Method of checking water ph. none
12) Method of adjusting water ph. none
13) Specific brand and N-P-K ratio for each bottle. 1/10 dilution urine, once a week
14) How often are you watering between feedings, and how much per watering? About a liter per day (not including sprinkler water, as this is unknown)
15) Any additives or tea's? No
16) Are your ph levels stable, or do they fluctuate? Don't know
17) What is your ingoing water's ph? ...your runoff ph? N/A, N/A
18) Do you foliar feed? If so, with what, how often, and at what time do you spray? No

Your growroom:
19) Indoors or outdoors? Outdoors
20) What size of closet, room or hut? Outside
21) What are the temps and humidity levels while lights are on? ...With lights off? No clue
22) Have you seen signs of insects in the growroom? Not on my plant

Your strain:
23) What strain are you growing? Sativa (likely some type of purp)
24) From seeds or clones? Seed
25) Is this an autoflower strain? No clue