Equation of motion for system of springs I need to find the equations of motion for the following system.

If $x_1$ is $m_1$'s extension and $x_2$ is $m_2$'s, then, I feel like for $m_1$ we just need to consider $x_1$ giving $$m_1 a_1  = x_1 K_C + x_1 K _B$$ because unless the extensions in both the left and right spring isn't the same, $m_1$ won't remain horizontal,
And for $m_2$, we just need to consider $x_2$ and $x_1$ giving $$m_2 a_2 = K_B (x_2 - x_1) + K_A x_2$$ because both the upper and lower springs exert forces on $m_2$.
But sadly, this isn't correct as this gives all 0 normal modes. Any help on where I went wrong would be really appreciated. 
 A: Too long for a comment, so in an answer:
Not all the springs are a function of $x_1$ and $x_2$, only spring $K_b$ is a function of both $x_1$ and $x_2$. 
Spring force is a function of how much a spring is stretched, e.g. how much difference er is between the beginning and the end of a spring, so $x_{begin}$-$x_{end}$ or $x_{top}$-$x_{bottom}$ for this case.
For spring A, the value of $x_{top}$ is fixed, so the spring force of A is a function of $x_{bottom}$ only, or in this case $x_2$.
A similar reasoning can be applied to spring C, which only has a variable $x_{bottom}$, which is $x_1$.
However, spring B has a moving $x_{top}$ and $x_{bottom}$, thus making this spring force a function of $x_2$ and $x_1$. You did recognize for your second equation, but failed to do so with the first equation. I have the feeling your making a mistake with positive and negative distances. Try to keep your coordinates consistent, and when in doubt, sanity check for physics. If, for example a mass moves, which direction will the spring force act? This is determined by the sign of the force in your equation.
