So I've been doing the S.P.A. for a few weeks and lost almost 13 pounds.
Chief, if we assume that your 'few weeks' is 2 or 3 weeks and you've already lost 13 lbs (even factoring in water loss) and that you only have 24 lbs more in order to break the 10% BF threshold, you're killin' it! Great work!
A couple things come to mind. Are you doing your weekly carb-up day? I'll spare you the details, but take it from someone who has learned the hard way, a weekly carb-up will greatly enhance your energy stores and keep you charged up through the week. My workouts improved, fat loss rate increased, diet was easier to follow, and, most importantly, I just felt better.
If you're following the TSPA diet to the letter, including carb-up days, then you might want to think about a slight bump in your macros to see if that makes a difference, just as Mark says to do if you find the initial macro set doesn't result in the expected loss. Everyone's body is different and, while the formula is a strong effort at building a precise model, no single model is universally applicable. A few more carbs or fat grams might be helpful to your body. If you find your rapid progress slows or stops and/or you're still not feeling better, you can reevaluate at that time.
Furthermore, the benefits of the improvement to your physical state might offset any potential downside (i.e. slower weight/fat loss) to your dietary change. You could find that added energy contributes to better workouts and a more active lifestyle to offset the additional intake. Even if your fat loss slows, just feeling better might make it worthwhile.
Hope this helps.