Couple things - you may have had the head too hot when you dipped it or left it in too long. I use a heat gun and for a 1/16th it takes a 3-4 count on each side before I dip it. I'll be the first to admit it I don't get them all right - I still get drip heads. One powder when it runs out that I won't buy again is the Dormant powder kit from Columbia Coatings. Didn't realize it was dip the color and all 5 colors even though the powder is the color come out looking silver - you cure for 10 mins then dip in the clear that comes with it then finish curing for the rest of the time.
Another color that's a problem child for me is Jann's white powder - I've thinned it out with clear and used a fluid bed and brush tapped and they still look bad. I went to white pearl instead.
Big one - Get yourself an IN OVEN thermometer they only cost $3-$4. There was a thread on Tackle Underground about this and in a bunch of different brand toaster ovens the temps were off anywhere from 10-40 degrees. I put one in my oven and it was off by 5 degrees.