They look kinds of urgly because what are you looking at are not pedestal subtracted and EDTM pulse signals are mixed into ADC. I plot a ADC distribution with EDTM cut and you can see that it is normal, although the amplitude is low due to the setting of S2m, which is 90% of signal from PMTs are sent into DIS for trigger and TDC, and only 10% siganls go into ADC.
Figure 1