you start always with the position vector to the masses . **Case I** $$\vec P_m=\begin{bmatrix} X \\ Y \\ \end{bmatrix}=\left[ \begin {array}{c} \left( l+x \right) \sin \left( \phi \right) \\ - \left( l+x \right) \cos \left( \phi \right) \end {array} \right] $$ the generalized coordinates are $~x(t)~,\phi(t)~$ from here the velocity $$v^2=\dot X^2+\dot Y^2 $$ and the kinetic energy $$T=\frac m2\,v^2+\frac k2\,(l+x)^2$$ **Case II** Position to $~m_1$ $$\vec P_1=\begin{bmatrix} X_1 \\ Y_1 \\ \end{bmatrix}=\left[ \begin {array}{c} r\sin \left( \phi_{{1}} \right) \\ r\cos \left( \phi_{{1}} \right) \end {array} \right] $$ Position to $~m_2$ $$\vec P_2=\begin{bmatrix} X_2 \\ Y_2 \\ \end{bmatrix}=2\,\vec P_1+\left[ \begin {array}{c} r\sin \left( \phi_{{2}} \right) \\ r\cos \left( \phi_{{2}} \right) \end {array} \right] $$ the generalized coordinates are $~\phi_1(t)~,\phi_2(t)~$ thus the velocities are $$v_1^2=\dot X_1^2+\dot Y_1^2 \\ v_2^2=\dot X_2^2+\dot Y_2^2$$ and the kinetic energy $$T=\frac m2\,(v_1^2+v_2^2)$$