I did have blocking diodes on the output of each panel because they were all paralleled to each other and I didn't want a shaded panel to pull from the others. Now I have a blocking diode on the output of each panel PAIR, but not in the series connection from one to the other within a pair. There are now four pairs (two on each side of the boat).

Regardless, the MPPT charge regulator would prevent battery drain at night. I think they all have that function, whether PWM or MPPT.