Gaussian process regression curves of 3C 84, using the light curves presented in Fig. 1. The minimum flux density shown in Table A.1 has already been subtracted. The blue data points denote the observations, the green solid line denotes the posterior mean, and the light-green envelope shows the 99.7% confidence bands. The dark-green arrow denotes the primary flare per frequency used for the time-lag calculation, and the dark-red arrow the secondary flare, wherever it was detectable.