Maybe start with a positive_ordered for the hard constraints as you do already, and then copy it to a new unconstrained vector and set
\rho_k=\alpha_k(\rho_2-\rho_5)+\rho_5,\quad \alpha_k\in[0,1],\quad k\in \lbrace 3,4\rbrace
for two new auxiliary variables \alpha_3 and \alpha_4.