Northern lights auto

Had to trim some leaves mid section on plant to increase air circulation. Feed her in the morning with about .0.6 l and again 8 hours later. Found some nasty looking leaves around top/ main cola. They look rusty and a faint yellow yellow colour. Could be a Phosphorus deficiency, or the stress of spending it's first day in grow tent. It's only on 2 leaves supporting main cola. Look at picture. If anyone can help with this problem I would really appreciate it. Think I missed last weeks journal, so this would most likely be week 9. Planted another AK-47 and OG Kush yesterday. Different diary. Second younger Northern lights looks healthy.