Lower leafs problems

If you're seeing the problem in the upper leaves, need to see a photo! But start this question over again by going to that diary and posing your question from the diary... add a photo of the upper leaves to your question... this will give everyone the MOST information and will help the community help you!

Thank you for your answer . Tho It makes me worried cause I forgot to mention it's only 2nd week of flower and I see it slowly moving upwards too. Because other lower leaves are starting to show the same symptoms.

Those lower leaves will almost always yellow-up and die off... it's no problem as long as the upper leaves are fine. I generally tend to snip them off when they get like this because they're not really contributing to the plant's overall performance. Now, if you start to see this on the UPPER leaves, you will need to figure out what's going on and take some remedial action... but for now, no worries! Best of luck!