Your plant looks sad. Looks over watered. Roots can't breathe.
Whats the pH of your soil, and what do you pH your water to before applying it? Do you check and monitor and adjust your pH before you water?
Lower leaves yellowing uniformly from tip to stem is nitrogen deficiency. But unless your pH is in range that nitrogen can't be absorbed.
If you don't have a means to pH your water, then i highly recommend you invest in a good quality one. maintaining proper pH is vitally important to your plants success.
If you've never flushed your soil, now would be a good time to do it. Excessive nutrient salts can build up around the roots over time and can cause the plant to have a difficult time absorbing nutrients through the salt. So flushing your soil at least once during a crops life cycle is highly advisable. Of course, flushing with 6.2 pH corrected water. Then allow for the pot to feel light before your next watering. Then water in a balanced flowering formula that is pH to 6.2 and your issues will resolve.