Hi all I’m in need of some advice. I have about 4-5 grows under my belt all in soil. I recently switched over to autopots as im away for work most of the week and they seemed a much simpler way to grow. I’m about 7 weeks into flower. During week 6 I noticed my ph range crept really high up over 8.3 at the rez. I have monitored it since and regular ph’d down within the ideal range. I knew nothing about ph fluctuations in these things…lesson learned. Since then growth has been really slow and i have starting seeing yellowing and rust spots on my leaves. I’m pretty sure I have some ph lockout. My question is how to fix this. They will flower for about 10 weeks and I want to flush and then go back to adding nutes to finish the grow long as they recover. Thing is ive read a bunch of conflicting info on how to flush these things. My grow medium is soil + perlite mix as recommended by autopot and im using ph stable clay pebbles as well. Water source is from the tap. Whats the best way to flush? Should i empty the rez and flush for a week with florakeen or turn off flow from the rez clean the tray and add ph’d water to that and let the plants drink that up and then slowly into nutes again?
Ph lockout in autopot
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@Smokeee 
Welcome to AFN Judging by the looks of your plants (dark forest green) they are getting too much Nitrogen locking out the Potassium. PH can be a problem in all forms of hydroponics but the first sign is usually a Calcium problem and not K which is what I am seeing.
I would just drop back on your fertilizer by 40% and look for improvement in the new growth. Be sure you are feeding balanced nutrients.
www.autoflower.org
Welcome to AFN Judging by the looks of your plants (dark forest green) they are getting too much Nitrogen locking out the Potassium. PH can be a problem in all forms of hydroponics but the first sign is usually a Calcium problem and not K which is what I am seeing.I would just drop back on your fertilizer by 40% and look for improvement in the new growth. Be sure you are feeding balanced nutrients.
Tutorial - A word on Nutrients
The proper use of “salt” based fertilizer to grow Auto Flowering Cannabis. Salts: Natural and man made any chemical compound formed from the reaction of an acid with a base, with all or part of the hydrogen of the acid replaced by a metal or other cation. Learning how to use salt based...
www.autoflower.org
@Mañ'O'Green i read somewhere that cal mag was the cause for a lot of folks ph fluctuating. And that it isn’t necessarily need this late in bloom should i cease feeding it that as well?
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All nutrients are needed in balance by the plant. Knowing what you have in the pot already is critical to maintaining that balance. study the tutorial the answers are in there.
I know this is an old post, but I had a similar issue. I found this if using Autopots and how to flush:
The only time you’d need to flush your pots is in extreme cases of overfeeding or nutrient lock-out.
If this happens:
Flush the plants via the reservoir
When it’s time for the final flush, you don’t have to directly flush your pots. Just add pH balanced water to your reservoir in the week or two leading up to harvest.The only time you’d need to flush your pots is in extreme cases of overfeeding or nutrient lock-out.
If this happens:
- Remove pots from their trays
- Pour several litres of water into them
- Allow to drain
- Restart at half strength feed
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This is for a basic flush, you want to do 3x the pots volume with a small dose of balanced nutrients. Like 1/4 to 1/8th the reccomended dosage at the correct ph. Don't flush with plain water as it will make your problems even worse. Best to not flush at all though
You did not mention what you are feeding. Are you just giving pure water to your soil (which could be too hot?), feeding base nutrients and/or bloom supplements; adding cal-mag?
Your using tap water could be the problem. What is its ppm and pH? Unless you have low ppm water, consider purchasing a small desktop reverse osmosis (RO) water filter system.
You might simplify everything by using RO (low ppm) water with Adv. Nutr. pH Perfect base nutes (MegaCrop base nutes are also quality chelated and in general don't need pH adjustment). Then you don't ever need to measure, much less adjust, pH. And if pH drifts in your reservoir, that's irrelevant.
Your using tap water could be the problem. What is its ppm and pH? Unless you have low ppm water, consider purchasing a small desktop reverse osmosis (RO) water filter system.
You might simplify everything by using RO (low ppm) water with Adv. Nutr. pH Perfect base nutes (MegaCrop base nutes are also quality chelated and in general don't need pH adjustment). Then you don't ever need to measure, much less adjust, pH. And if pH drifts in your reservoir, that's irrelevant.
