I have a sativa plant that is 3 weeks into flowering and her leafs started turning yellow out of no where as well as 2 other indica plants ,IDK the ph level since I don't have a meter but if it was a water problem then all my other plants would do the same ,I think it's a nitrogen deficiency but I would love the help of this community to help me correct this problem
@ptbgrow Normal enough for the plant to consume and discard the oldest fan leafs as she enters full flower. Let em run and do nothing different. Growing outside you really need to treat for caterpillars with BT once a week and your good to go. BNW
If you look there are dozens of threads created by people who in the third week of flower start getting some yellowing and freak. I personally have found that starting a bit of MgSO4(Epson) a couple feedings before flip and continuing almost to the end reduces this yellowing a bit. I also continue my veg nutes until the stretch is over so they are also getting a little more N for a couple weeks.
Another thing alot of people do is start flowering nutes at the beginning of flower and the plant is actually still vegging the first 2 to 3 weeks during the stretch, i always keep with the N during the first few weeks of flower. You could get some espoma bat guano or worm castings and amend it into the top of the soil and that will help give you a N boost through the rest of flower.