I don't work in Fahrenheit, but think your TC readings are quite low - would be surprised if you got to SC at 399f.
I'm not an expert by any means but "normally" SC would come 20 or so degrees later.
I haven't got any sweet blue (would love to get hold of some) but have been roasting a Brazil Natural Corrego. I agree with Dave - that extending the roast will help - I give it a good minute and a half soak time and then bring on the heat gently. This gives me a longer drying time - but I find the beans are quite delicate and need this.
Anyway here's a roast I did yesterday to Illustrate. I've converted it to Fahrenheit...
I might add that I also pre-warm my beans.