Try using some ph up or ph down from canna. Try that and see if it helps if you haven't already. I don't usually have this problem as I get my water from a natural spring and it's pure. Just behind the house and thru the woods a bit. My ph usually stays between 5.5 and 6.0. I've also uploaded a pic of my current clones, check out my other posts for pics of my budding ladies. Hope this helps a bit. Peace and God Bless!
P.S. Here's a piece I got from a google search for ya, came from grasscity.
By someone named. Growbot
There are many types of rooting mediums that are available to the gardener. The ones that we are focusing on are: rockwool cubes, Rapid Rooter plugs, Oasis cubes and aeroponic cloning systems. For aeroponic cloning systems (e.g. EZ Clone, Power Cloner and Clone Machine), see “Water Quality”. Rockwool cubes need to be pre-soaked at a pH of 5 prior to placing the cuttings into them (or use Rockwool Soak). Keep the cubes moist but not saturated with water. Once you pour the water onto the cubes and have allowed the excess to drain off, gently squeeze each cube thus making it release more water. If the cutting stays too moist it will have a higher chance of rotting. Rapid Rooters and Oasis cubes are ideal products to clone in as both of these mediums hold less water and allow more oxygen in than the rockwool cubes.
