  Motivated by recent experiments in Ba$_{1-x}$K$_{x}$Fe$_{2}$As$_{2}$ {[}A. E.
B\"ohmer \textit{et al}, to be published{]}, we analyze the type of
spin-density wave (SDW) order in doped iron-pnictides and the discontinuities
of the superconducting transition temperature $T_{c}$ in the coexistence phase
with SDW magnetism. By tracking the magnetic transition line $T_{N}(x)$ towards
optimal doping within an itinerant fermionic model, we find a sequence of
transitions from the stripe-orthorhombic ($C_{2}$) SDW order to the tetragonal
($C_{4}$) order and then back to the $C_{2}$ order. We argue that the
superconducting $T_{c}$ has two discontinuities -- it jumps to a smaller value
upon entering the coexistence region with the $C_{4}$ magnetic phase, and then
jumps to a larger value inside the SDW state when it crosses the boundary
between the $C_{4}$ and $C_{2}$ SDW orders. The full agreement with the
experimental phase diagram provides a strong indication that the itinerant
approach is adequate to describe the physics of weakly/moderately doped
iron-pnictides.
