Thanks for all the replies! I think a good cleaning is #1 cause after I had 1 bad batch, it was 0% for the next 2yrs.
Honestly surprised nobody mentioned aloe, I swear, just go get a beefy plant from a garden store (orchard supply, home depot, etc) get a big spear, squish it up until the gel is squeezing out of it, and after preparing the clone tips, smear it in there and let it sit inside the spear for about 5 seconds, plant in pre-soaked rockwool cubes, ( soak them in a bucket with a TEENSY-TINY bit of worm castings, tiny, tiny pinch of kelp, and aloe) and use a heating mat under your cloning tray, I use ONE t5 (24 watt I think) and I fill the bottom of the cloning tray with spun coconut fibers (the big stuff looks like donkey hair), then on top of that I put the rockwool/clones, it keeps them from sitting in the water, and you can add a lil water to the bottom of the tray without saturating the clones, in doing so, that in conjunction with the heating mat, slowly evaporates the water making the air VERY humid, but the rock wool not wet. Don't need to spray, cept maybe once a day, depending on your heat)
I used to have oversaturation issues (like the slime you mentioned)
Perfect for roots, and you hardly need to spray them because the humid air is enveloping them in moist air.
Then the remaining aloe you squeezed up you can suish throrughlt in about a quart of water, strain, then put that into a spray bottle, then you have an aloe spray to mist them with.
I used to have about 50-60% success rate with clones, until I got a heating mat, did the coco-hair, underneath, and used aloe, now i'm at 90-100% success rate.
also important to NOT squeeze the rock wool, in case you didn't know that.