FIR luminosities versus CO line luminosities of our three QSOs (coloured squares), the literature sample of z ≳ 6 QSOs (filled, coloured circles), the z > 3 SFGs in Table A.2 (orange circles), the z ∼ 1.2 star-forming galaxies and AGN from Valentino et al. (2020; orange and blue triangles), and the local (U)LIRGS, AGN, and QSOs from Rosenberg et al. (2015) and Kamenetzky et al. (2016; grey, right-pointing triangles). The z ≳ 6 QSOs follow the literature relations for the CO(6–5) and CO(7–6) transitions but are shifted to 2–6× lower CO(2–1) line luminosities than predicted by these relations.