I agree on the not blasting em with light and that being a very common mistake. But I wouldn't put em in darkness as clones are usually mature and can trigger flowering. I haven't tested a short duration but with 2k lux I hardly ever get any yellowing or clones that are not a nice green by the time they root unless I leave em to long or the cutting was not so healthy.shut off the lights for the first day of so let them relax most folks think you need to jam them under lights asap but think if someone cut off one of your appendages would you want to be under a bright light? Plants use light to grow of course but in thsat process they loose moisture via the leaves but clones have no roots to replace it thats why you need high humidity in the clone chamber if they have no light they sleep give them a day or so to rest not ad stress on top of stress then go with the light schedule you desire.
cloning is not hard people make it hard by trying to nurse them to much you should be able to have 100% success every time without any fancy stuff a bottle of cheap stim root and water