what are your temperature and humidity levels? you want 70°-90° Fahrenheit and 50%-70% humidity in vegetative growth and 30%-50% humidity for flowering. what is the soil/soiless mixture you are using? what nutrients are you feeding and how much of what? what are you adjusting the pH of your nutrient mixture to? you want pH 5.8 for hydroponic and soiless (peat moss and coco coir) and pH 6.5 for soil. are the buds that the pistils have withered on in front of your fan? what is the pH of the first runoff from your pots when you water? yellowing of the bottom leaves is normal during flowering. the brown patches on your leaves is a deficiency and does appear to be a phosphorous deficiency but without being able to pull your plants out of your tent it will be difficult to treat. it does look like your plants have released pollen and seeded themselves.
here is a nutrient availability chart
here is a cannabis leaf deficiency chart
here is the Cannabis Plant and Pest Problem Solver and the Plant Abuse Chart
Cannabis Plant and Pest Problem Solver - Pictorial
Plant Abuse Chart
here is a nutrient availability chart
here is a cannabis leaf deficiency chart
here is the Cannabis Plant and Pest Problem Solver and the Plant Abuse Chart
Cannabis Plant and Pest Problem Solver - Pictorial
Plant Abuse Chart