Brown spots down the veins of leafs

High bro, It is difficult to help someone without pictures. But most problems with cannabis are due nutrient lockout caused by overfeeding. If you want to know if it was caused by overfeeding you can flush the soil. And start giving lower amounts with nutritions after (start with 50% of what you gave previously). I would flush only 1 time and you can do this by slowly pour water onto the top of the soil, allowing it to drain freely from the bottom of the pot. Pour slowly, so the water doesn't overflow from the top of the pot. Use approximately four times the pot's volume in water to flush the soil. For example, use 1 gallon of water for a 1 quart pot. After the flushing you want the soil to dry out (almost) completely. After this you can continue watering like you are used to and start giving a small dose of nutes again. Goodluck and Happy Growing! 😋

You don't have a diary, you don't have pictures, you just tell us about some brown spots... we aren't wizards here, we can't see the unseen or know the unknown. Either give us information in terms of a diary WITH pictures or take any bit of random advice from someone on the street corner. Seriously, what is it you expect? We WANT to help but with a simple description of "brown spots" we have about as much chance of giving you good advice as we do of winning the PowerBall. Let's see a diary and we'll go from there.... Cheers

Feed them every 4 days on bio bizz top max and bio bloom. Feed them 2mg of each per litre. PH of water is 6.8 and they are in compost.

Got any pictures? what have you been feeding and how much/often. Do you PH your water. What are you growing in. could be anything without that info. My guess is to much food.