yellowing in the lower leafs are perfectly fine your plant is just focusing on producing nice fat buds :) i know in the end of the flower the plant uses nutes from the leaves from the whole plant but right now its just taking some nutes from the lower older fan leafs so no worries. i also think this is why some people say dont defoliate so much cause your plant uses nutes from the leaves thru out the whole flowering stage. plant is smart they will do what is right for them also 13 C should be totally fine as long as its not a frost temperature they will keep going just fine unless they go from 57 C to 13 C then thats a different story sudden change of temp can shock the plant. but overall your plant is doing fantastic :) the buds already look super yummy
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