HELP FAST! What is this brown stuff I'm wiping of my cuttings causing them root very slowly

Using dewey mister to clone, the bottom 2 inches of cutting is getting this grown gunk on them and they are rooting like 3+ weeks later. If you don't know the dewey mister is like a bubbler I guess where the bottom 2 inches of the cutting sites in water.

If you look at pic 1 of the open lip (top left of it) you can see the brown dirt. This stuff gets on the bottom of my cutting and that's what I wiped off in the first post. Everything is always clean, I would get a very small amount of this, but this is the most I've ever got.

Anyone??

Are you using well water? I think it could be from a high mineral content in your water. You'd have to have your water tested to know for sure.

Probably brown slime

What kind of water you using in res?

You can get a product called iron x. Its primarily a cleaner but when it comes in contact with iron it turns purple. Spray it on the paper towel and if the brown streaks turn purple you know your dealing with a high iron content in your water.