Yellow/Dry Clones, can anyone help?

Hi there, these clones were recently transplanted into a hydro system using cutilene slabs, they were looking really healthy when they went in with lovely roots but after just 1 week in the hydro the lower leaves have become all yellow and dry with a lot of them falling off, also growth seems to be minimal which isnt normal for this system, im used to seeing the baby's flourish in there, but not this time :? Does anyone know what the problem may be? or how to rectify it? Cheers.
additional info:
They are in an auto Fed eco system, plenty of ventilation, constant 80 degrees but cant get humidity above 40% for long at the mo. i know PH is too high at 6.8 but my mate has my level meters :( Last time i checked E.C it was 1.5, about 3 days ago.
Thanks again
https://www.rollitup.org/members/greenfingeredman-153008-albums-bad-ones-picture67964-clone1.html
https://www.rollitup.org/members/greenfingeredman-153008-albums-bad-ones-picture67963-clone.html
https://www.rollitup.org/members/greenfingeredman-153008-albums-bad-ones-picture67965-clone2.html
 
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