Yellowing leaves on bottom and middle

It definitely looks like a nutrient deficiency, as the yellowing is progressing from the bottom to the top of the plant. This pattern usually indicates a deficiency rather than a nutrient lockout. A nitrogen deficiency is a likely cause, since older leaves are typically affected first. However, it could also be the onset of a CalMag deficiency, especially since there’s already a brown spot appearing — a potential sign of calcium deficiency. It would be a good idea to check how much calcium and magnesium you’re currently supplying to the plant. Look up the recommended values to make sure it’s getting sufficient nutrients.