Brown leaves and red stems. Is this a calcium deficiency ?

Hi, Also phosphorus deficiency would cause all symptoms. Check here: https://www.growweedeasy.com/cannabis-plant-problems/phosphorus-deficiency In order to solve these kind of problems a good flush with the PH water and then a good feeding is just what you need. Please note that you might be feeding the correct amount of nutrients but the plant might not be absorving them. Checking the EC of feed water and runoff water can also hint you these things.