AAVSO observations still come from only *one* observer (Josch Hambsch, HMB): https://app.aavso.org/webobs/results/?star=ASASSN-21gk
Recent ASAS-SN Sky Patrol (Shappee et al. 2014ApJ...788...48S and Kochanek et al. 2017PASP..129j4502K) light curve and data:
Spectroscopy as well as time-resolved and multiband photometry are urgently required.