Yellow Leaf

If it starts at the TOP its a IMMOBILE mineral issue. Ca , S , Fe , Cu , B If it starts at the BOTTOM, it's a MOBILE mineral issue .N, P K Mg Semi mobile ...Mo Mn Zn .These ones are listed in several legitimate publications as mobile and then other legitimate publications immobile, so I consider them semi mobile. In MOST publications, Mo Zn and Mo are listed as an IMMOBILE Mineral. So I would rule out the rest first if you can, but leave room for Zn Mo or Mn on both sides. I can't see the bottom of your plants, but to me that looks like Magnesium deficiency. If it's not in the bottom of the plants I'd look at Copper deficiency. Either way I'd flush with proper PH and PPM H2O. Also, check your light LUX and make sure your light isn't to close to your canopy, and check your PH. Most likely what every the deficiency is the cause is incorrect PH. If you are growing in soil check your run off, if rdwc check H2O. Make sure your PH is correct for flowering. Calibrate your pen. Best of luck! Deficiency Intervienal chlorosis on older leaves (as opposed to iron deficiency, which appears on new growth) Irregular rust-brown spots on leaf margins, tips, and between veins Symptomatic leaves curl upward Sickly plant with dying and dropping down turn leaves Excessive levels of Calcium, Potassium, and Aluminum can lead to Magnesium deficiency, as well as too low of a pH. While magnesium deficiencies primarily manifest during the flowering phase, they can also occur in the vegetative phase when nutrient ratios are imbalanced. Magnesium deficiency symptoms may appear similar to potassium and manganese deficiency symptoms however, manganese deficiency symptoms usually occur first in younger leaves compared to magnesium and phosphorus deficiency symptoms first occurring in older leaves.