I'm gonna guess you're doing cardio very close to strength training? Right? Thats one cause, you're killin your CNS. Now if you're restricting calories for weight class, then I'd say your losing some muscle. I honestly feel that your karate is more than enough cardio. Your body only really needs 20-30 minutes of intense training and it continues to work for hours afterwards.

When I was cutting a month ago, I actually got stronger as I lost weight. Getting ready to cut again in a week. i split my cardio and weights. Cardio in the morning and weights at night.