I never understand the differences we see when using basically the same things. Water, nutrients, growing medium, and growing systems can be all the same but we see differences in pH, EC, clogs, and cleanup. We see it all the time, one person uses MC and their pH creeps up while another uses it and the pH creeps down. I have used rainwater, hard tap water, and distilled water with Advananced, BioTabs, Technaflora, and Greenleaf nutrients and only problem I ever had was the occasional clog, which were worse with AN than any other nutrient.
My personal favorite is fresh rainwater when I can get it. Where I live it comes down at a neutral pH of 7.0 and an EC of 0.03 or pretty much zero. Distilled water causes way too many pH issues for me and costs electricity to make and my tap water at an EC of 0.44 or 220ppm while not the worse has to be bubbled for the chlorine and treated for chloramines before you can use it. But I have used them all without scrubbing my trays and most I have ever taken to an autovalve is a toothbrush. Mind you my trays are not brand new black anymore but they do what they are supposed to. I tried to go cheap with some bargain 1/4” tubing once but then just purchased 50’ of what Autopots sell and have had fewer clogs for it.
I look forward to your pics of this cause I can’t imagine how this is happening to you. My worse cleanup on an autovalve was after I let the algae go wild in my tray out in the greenhouse. Yuck!