I am not sure what you mean by "developer staining". What colour is the stain? Where is it present on the print/paper? What type of developer is being used? What temperature? When does it appear?

I have had some issues with pinkish spots appearing in a print. They were related to the temperature of the paper when being coated (too cool) as well as the temperature of the coating rod (also too cool). I found that by slightly warming the solutions (I use a coffe cup warmer) and the rod and paper, the spots went away. I have a feeling that they were caused by palladium coming out of solution upon contact with a cool surface. Other than that I have never had a stain of any sort on any type of paper I have used.

I have never used ethyl alcohol in my coating technique. I am not familiar with the produuct but understand that it is used to "thicken" a solution, making it easier to spread on a surface. This is a different action to that of Tween or other surfactants that actually reduce the surface tension of a sulution and thereby fascilitate penetration into a porous surface.