Hey Pan
I may be completely wrong on this but I don't think the nutes are the problem...I think my ppm meter was telling me wrong and the plants ran out of nutes. The reason I'm thinking that is last night I added a very small dose of nutes as a sort of test to see how the plants would react. You are quite correct that they look pretty off today, but they looked worse beore I added some more nutes. I'm going to keep a very close eye on them tonight and tomorrow before I start freaking out. If things haven't perked up by tomorrow evening, I'll get with you and see what you think. The top new growth looks very green and healthy, but I am concerned about the overall health of the plants. Just have to use a little patience.
Also, is there any chance that the Pyrethrum has caused the droopy look...extra weight on the leaves, perhaps? I really sprayed the hell out of them and a slight sheen has appeared on the leaves, which seems like possible residue to me. Just an idea.
It does sound like your ppm was throwing a wrench into the works. Keep and eye on the plants and mix some nutes following the nutes directions don't worry about ppm just get the ph straight.
Yes that does leave a film on your plants but that keeps the mites away and the droop was caused by it but don't worry your plant's will be fine.
Pan4