Received clothes that are yellowing

I strongly suggest you start from scratch with these if you're going to attempt to save them. I saw that you received them in this condition so you don't really know what caused this deficiency. Get new cubes(Rockwool), clone powder or gel and gently remove the old cubes as to not damage any root growth (if any), re dip the cuttings if you don't see growth or hardly any growth then replant in your new wool cubes. I recommend you don't soak the cubes either as they hold a lot of water and will easily drown young plants. Start off with minimal nutrients, mainly root inhibitors only and crank your rH up. I hope this helps.