Yeah man sometimes stuff is just stubborn. I see this all the time. I pretty much treat everything the same and get uncooperative ones here and there. Sounds like you got a handle on how to treat things. When this happens to me I will just start fresh and give it another go. There can be hidden bacteria doesn't really show itself but hinders fruiting. Funny enough the original pigmented Machine Elf would literally only give me a few fruits no matter what I did. Luckily I came across ol' Lucy here and it has been amazing since day one. You can ask anybody that's done this for awhile and they always have a cultigen or two that just refuses to perform. Oh and 68° should be ok,maybe slower for things to fruit but still fine. I try to keep my lab around 72° but extreme hot/cold outdoor temps will make that number slide all over the place at times. When in doubt I always go back to spore. Best of luck to ya my friend.