Detect signals degree of imbalance
One thing that can be useful in condition monitoring of rotating machines when rotation angle is important is to look at using circular or directional statistics.

Suppose your measurements are:
$$
m_1(n), m_2(n), m_3(n)
$$
for the three moments $m_i(n)$ for $i=1,2,3$.

Calculate the instantaneous directional mean of the moments:
$$
m_{\rm tot}(n) = \left ( m_1(n) + m_2(n) e^{j2\pi/3} + m_3(n) e^{j4\pi/3} \right)\\
\bar{\phi}(n) = \arg \left(  m_{\rm tot}(n) \right)
$$
assuming that the first blade is your reference.

This direction, $\bar{\phi}$, is the direction of the average moment.  If it's always aligned (or "anti-aligned") with one particular blade of your turbine, then that can indicate your "problem blade".

You can use the magnitude 
$$
\left| m_{\rm tot} \right|
$$
as a measure of how "out of balance" the turbine is, as this should be (close to) zero most of the time.

If you have the azimuth angle, $\theta$, then you can get fancier. It may be that you need to angle-align (rather than time-align) your measurements to pick the faulty blade.