These are G2926B clear glazes with stains added and fired at cone 6. The one on the left has 11% Mason 6021 encapsulated red. It is pebbling the surface (even with 2% zircon), it may be at the upper end of its firing range. Possible solutions are faster firing up and down to give the stain less chance to decompose. A lower percentage might help, that would impart a bit of variation where it is thicker and thinner (like the purple one) to add visual interest. A different host glaze, perhaps one with less boron might work better. The purple one has 10% Mason 6304, it is not affecting the glossy glaze surface. But the percentage needs to be higher to prevent the wash-out of color where it is applied thinner.
This is a type of stain manufacture that enables the use of metal oxides (like cadmium) under temperature conditions in which they would normally fail.
Ceramic stains are manufactured powders. They are used as an alternative to employing metal oxide powders and have many advantages.