you need to tell us what you are using for lighting . I did that to a plant when I wanted to pull massive yield from a bud it would burn leafs like that . but I trimmed them off. so it would not look nasty. 6 weeks in . Is it a 8 week strand ? if so its to late to do any thing now time to flush it soon in a week or so . so just keep doing what your doing trim off those nasty brown leafs they will get into the bud make it look like shit when its dry. and start your flush next week.