I don't know what you mean by quantum core, but there are particular chapters (scattering theory is an example) in a what Americans call <graduate> course on QM which are mandatory prerequisites before jumping into quantum field theory, the latter being defined as the formal gathering of facts giving you a description of the Standard Model of Fundamental Particles & Interactions.I have completed Quantum Core courses as well as GR and it seems there is something I am missing before taking QFT/QED courses. Is there another subject between?
I don't understand. How could you have had QFT and QED separately and with different levels of difficulty ?I found a QFT course that picked up right about where I needed to be. I think the problem was that courses labeled QED were a bit further ahead than I was ready for.