We have measured 2s–2p fine structure transition energies in highly charged Ni, Zn, and Ag ions using beam–foil excitation and grazing incidence spectroscopy at the GSI–UNILAC accelerator. The precision of the results provides tests of two-photon QED screening corrections to the 2s–2p transition energies. The experimental values are compared with other measurements and with recent relativistic calculations along the lithium–isoelectronic sequence.