Is there more of a problem with yellow? Should I be using something on the yellow? HELP> Sometimes the yellow is clear, but mostly a little cloudy.

I fuse 3 or 4 shelves and slump the same in a skutt kiln. I fuse to 1490 and slump to 1300. Any ideas?
Once, I put the yellow glass on the bottom shelf and it came out really clear, but another time I did the same thing and it came out cloudy.