Help please: old growth turning brown..

[LOC NAR on probation]

Looks like nute burn to me BUT What kind of tap water and what is it's PPM before you add anything ?
Chlorine, chloramine burn from tap water Looks like lock out or nute burn. Flush with R/O or distilled water for a few days and stay away from tap water unless it's from a well and you know what's in it. It's better to start with nothing in the water and add only what you want.
Your ec would only be 1.2 to 1.6 and depending on the meter to covert to ppm's would be 800.

[Esteban1]

Tend to agree with Mal420 & LocNar.... Def ph related. Remember, "it's a weed". Possible there is way too much "over thinking this"?

Sic Semper Tyrannus

:wtf:

[low_rdr]

First time I've ever been messaged to check out a thread before!

Okay - I see your using perlite as a medium, but there are some issues. First is the lack of a constant water supply. I understand your feeding schedule, but your medium does not hold much water, so when your done feeding, that perlite drys out quickly. Second, for pure hydro flowering, you should be looking for a steady PH of 5.5 or 5.6, not between 5.2 and 6. Too much variation, remember, when troubleshooting problems, KISS (keep it simple stupid) - The less variation, the easier to pinpoint.

Third, your light spectrum is all screwed up for flowering, you need more 2700's in there, 4100's are close to a neutral light (5k is neutral) so they aren't doing you much good (please note, I did not say they aren't doing you any good, just not much, more or less wasting power on those) If you want a proper spectrum, keep the 2700's and toss in some 6500's, and use the 4100's in your bathroom.

Forth, why are you starting seeds in soil, and then putting them in hydro? (they're faster in hydro) (this isn't troubleshooting, just a tip)

Okay, now that we got that out of the way, lets see what we can do.

judging from your troubleshooting post your only using dutchmaster gold for flowering. I think your a little short on your phosphate. This ISN'T ONLY a PH issue. Also, stop cutting your leaves, your not stopping it, only stressing the plant more.... stolen analogy: How would you feel if you had a fever and someone chopped your arm off? Anyway, in flower the plant needs more phosphate and potassium than your currently giving it. 800 PPM is also a touch low for flowering, I'd slowly increase to 1200, looks like your a few weeks in, so maybe skip that part for now, 800 is great for veg, but in the future you do want to raise that a bit when flowering, as they eat more. Test the PPM and PH of your runoff, and give those both to me as well (PPM and PH in, PPM and PH out, give me both sets of numbers after you correct everything else)

On to other possible problems, your plants are super small for the amount of light they're getting, and I have to defer away from a PH lockout and go with dry roots to solve this one. increase your water time from 6 hours to 12 after slightly adjusting your PH and adding in a better balance of nutrients. I won't suggest you pull them from the perlite to check the roots, wait until after the grow is done.

If you don't have air in your water, and your just submerging your plants, add in a touch of hydro peroxide (its just oxygenated water more or less) 2 tsp per gallon will be plenty. If your still having problems in 3 days (the browning continues) let me know, and make sure you add picture updates in a few days as well.

[polishpollack]

Overfert, and use potting soil next time. Don't feed so much. Maybe raise the lights some to get it to grow taller. 5.2 is a little too low, even for what appears to largely be a hydro grow. Just potting soil and you won't have to worry about pH anymore. If you want to stick with perlite, pH around 5.7 should be fine, but it will fluctuate. Look more at your ppm and determine if pH is rising because ppm is dropping. If so, probably need more fert and keep an eye on that. Soil is an easier thing to do.