In any series highest melting point is for VI B group elements, due to the presence of maximum number of unpaired electrons that gives strong metallic bonding.

If you look at values, Mn has a lower value than other elements of the period. The melting point depends on the extent of metallic bonding, and the idea of metallic bonding can be understood by the enthalpy of atomization values.
Secondly, the electrons in the half-filled d orbital are strongly connected to the nucleus. Therefore, The element belonging to this group. (Cr,Mo,W,Sg) have the maximum number of unpaired d-electrons (${\mathrm{d}}^5$ configuration). Therefore metallic bonding is the maximum and so are the melting points

Hence, group VI B elements have a higher melting point.