Hi! Pura Vida! 👋
Buddy to me look like a Magnesium deficiency According to... (Cockson et al., 2019, p. Initial symptoms developed withslight yellowing of the interveinal regions of the lower and older foliage).
You can add a Mg or a CaMag suplement with you regular type of fedding,for fix the deficiency. if you need more information about nutrient disorders, you can read them in "Characterization of Nutrient Disorders of Cannabis Sativa"
More info can be useful, week, medium do you grow and general picture of the plant to see better
Bye and many successes!💪
References
Cockson, P., Landis, H., Smith, T., Hicks, K., & Whipker, B. E. (2019). Characterization of Nutrient Disorders of Cannabis sativa. Applied Sciences. https://www.mdpi.com/2076-3417/9/20/4432