Glaze firing

I did my first glaze firing in almost a year. The results were mixed but at least no disasters. I fired to a top temperature of 2170 with a 15 minute hold and got a cone 7 according to the witness cones. So I guess I overfired. I have been combining a cone 6 clay with a speckled clay about two-thirds to one-third. I had glaze faults and I am guessing the specks are dissolving and not gassing out and the glaze is not healing over due to the overfiring. Some glazes this was a problem and some it wasn't. I'm guessing the top temp next time needs to be lowered and/or I need to discard the speckled clay.

The bottom pictures are of Raw Sienna. I like the way it pools and breaks on texture. I may have applied to thin, but this glaze shows the faults from the overfiring. On a test tile without the specks it showed no glzae faults, so I'm guessing it's the speckled clay causing the problem.