Could just be preflowers. Clones are already sexually mature as the plant they were taken from.
(Can you even clone autos though?)
Is the PVC pipe in your country more of a hollow core or porous type material maybe? Here its solid, but ABS is whipped up with air bubbles and more like a foam for example. I've seen foam core PVC though in other prodects, so thought I would ask. In Africa right?
It looks like that's the only part that is stained is the end of the pipe, and not inside or around. Is that what you meant? Not sure how you would ever get slime with 17c water, with or without adding bleach, and especially in the first 5 days..