Yellowing leaves

Did you check soil ppm before planting? It can be hot soil. To check that, take small amount of soil (100 ml), pour 100 ml of ph-neutral or ph-balanced water, test runoff. Coffee filter works well to make sample clean. It shouldn’t be higher than 800 ppm. The less is better. My last grow I bought hot soil with EC 4 (2000 ppm). Had to flush hard, and the whole cycle pH was off, probably because of too much lime in it. First few weeks I had massive disorders. Then, she almost recovered as soon as pH went to 7.5 and lower. First runoff was pH 8. The worst soil I’ve ever bought..

Well, first of all, for an autoflower this age, you shouldn't be giving any nutes whatsoever! They don't like a lot of nutes, especially when they're young so they really don't need a thing until they're at least 2 weeks old - and then you give it to them VERY slowly - 1/4-1/2 strength to see how they're going to react. Dosage can increase the next week but you really need to take it slowly! As for your nutes and the pH swing... yeah, it's your nutes and Creepy_Steve is spot on about that. . But beyond that, why are you saving the nute solution? Are you really trying to save money by saving a teaspoon of some nute?! Throw away the stuff you've mixed up that you don't use! But just give them plain, pH'd water for the next week anyway... and try the nutes (1/2 strength at the most!) after that. Good luck!

if your nute's pH drifted that much in 1 night, it's your nutes.. they aren't buffered properly. choose a different brand and avoid the headaches of an unstable mix of molecules... they neglected to hire a proper chemist, i would assume. As a point of comparison... i refill my 55gal rez after each irrigation (18-24gallons used, depending. In 2 months i have yet to empty and clean it out. I have not once had a pH swing, because my nutes are a professional AG product and not some dopey marijuana brand created by what i assume are anti-intellectuals that didn't do the proper research to make a resepectable product, BWAHAHA. honestly, the marijuana-focused nutrient lines are all a joke.. they are overpriced for teh exact same ingredients you'll find on other products available.. Look at "Athena" or "Floraflex" nutes... i spen 0 on 2 25lb bags and an 8lb bag of epsom.. it's lasted nearly 4 years (25-30 plants/year)... do you spend more than 20-25/year on nutrients? there is no reason to.. these ingredients are ubiquitous commodities.. they are not mystical, magical ingredients. they are akin to Rx generics -- molecularly exactly the same, therefore function exactly the same.. cause and effect that is undeniable. double check callibration of pH pen, of course.. rule out simple stuff before going nuclear on your nutes. want to use them up before you swtich? get some 5% white distilled vinagar (acetic acid), you probably have some around house. Citric acid is what they price-gouge you for in a "ph-down" product. 3usd for 5 gallons of vinegar... get some 3mL pipettes for easy and consistent measurement... whatever it takes to balance it out should be similar as long as the starting ph doesn't shift on you.. pH is a log scale, so just basic math to calculate and 100% predictable... trial and error will get you there.. do 1mL at a time until it is proper pH.. now, you know how much to add 'next' time.

Your problem is that the roots are suffocating because of overwatering. Let the soil dry out till the top layer is completely dry. Then give water again but not so close to the plant. Let the roots search for the water and when you do this the other roots got enough acces to oxygen. 100 ml should be enough and at least 5 cm away from your plant. The larger the plants grow the more water you can give and each time further away from the plant.

Hi yes it's normal for premixed nutrient solution to change ph when left for even a day n reused I ph everytime I feed/water whether premixed or not also its quite early to start feeding such a young plant nutrients I usually start under half of recommended doses on day 14 I would just feed correct ph'd water with a tiny bit of root nutrients for now I hope this helps 🙏