Mine look like that too -two strains- but I have several minor probs..so I can't put my finget on the issue. I was attesting it to ph probs (can't ck yet) but you say your ph is good....I also have variable temps (in my furnace/water closet) and was in the line of thinking that had something to do with it (still only a 10 degree vary which is supposed to be okay according to the grow faqs). I also have soil with nutes in it..... I'd like to know the definitive answer to this as well. If I figure it out, I'll let you know and vice versa please. S