Brown spots

I had the same issue with my LSD-25 plants this time around too. Stems and stalk turned purple, spots on the leaves. I think the purple issue was from a new stronger LED light and the spots from under feeding. The buds are looking good at 55 days but my plants look ragged and abused. I raised the light, increased Cal-Mag and new growth came in green. The older leaves still have spots. Thanks for sharing your photos, you have helped me as a novice grower.

https://dutch-passion.com/en/blog/a-visual-guide-to-cannabis-deficiencies-n987 First thought P-K, Looks a lot like Manganese deficiency as well, although that seems to be less likely compared to a P-K deficiency. Good luck.

Ola amigo, parece muito uma deficiência de cálcio. Sua planta de cannabis pode mostrar sinais de deficiência de cálcio se o pH nas raízes for muito baixo. Isso ocorre porque quando o pH de sua zona de raiz é muito ácido, sua cannabis não consegue absorver o cálcio de forma adequada através de suas raízes. Portanto, o primeiro passo é garantir que você tenha o pH correto para o seu meio de crescimento. As deficiências de cálcio e magnésio costumam aparecer juntas na cannabis. Muitos produtores decidem comprar algum tipo de suplemento de Cálcio-Magnésio (frequentemente chamado de Cal-Mag ) para o seu quarto de cultivo, caso essa deficiência comum apareça. Boa sorte no cultivo e abraço

I was thinking maybe potassium deficiency? Never personally experienced it but looks like what I’ve seen in books for K deficiency. Or consider fungal or some disease

Id guess its either calcium deficiency or its a fungal infection.