What is the issue with my leaves?

your ph may be off, but you also should add cal mag if you havent already, i recommend flush until your run off is at 6ph, wait for the soil to dry out and your first couple feeds you should use a mix of cal mag and kelp. 1tbl spoon per gal of each. you should see an improvement on the plant, also cut the yello leaves off, your growing for bud and you want the plant to focus on good growth, you dont smoke those leaves and the plant is trying to send energy to the leaves that are going through problems, this can affect your yield come harvest time. so cut those off and move on. your plant will be fine, cannabis can take a lot. so cut off yellowing leaves, flush, test run off until 6ph, add cal mag and if possible kelp. feed a few times, then start feeding again and adding cal mag and kelp with nutrient mix, it will be ok