Bubble slime on my cuttings stems

Hey guys I have taken cuttings and placed them in my homemade cloning system. Basically I have a tub with water (phed rain water + a pretty high amount of h2020) with a air stone on a heating pad keeping water temps at 20c and room temps are steady at 90% RH and 23c. I have my light hanging 30cm from the plants tops. I have now 3 days later discovered what looks like white bubble slime? Can you guys just help me by resolving this if it is a big problem? There is a lot of cuttings in this setup.