Dagan was the head of the pantheon comprising some 200 deities.
The fact that Dagon was the head of other gods doesn't change the fact that he is a SINGULAR god who was called by the plural word "elohim".
Ashtoreth is called the "Face of Ba‘al" which ties her directly to that false god.
Molech I have no certain info about but it seems false gods were associated all as one to God since all are false and likely inspired to the greatest false god-wannabe, satan.
Pharaoh was also called by the plural word "adonim" (lords), even though he was not a person within a "Pharaoh-head".
In Genesis 1, one of the persons of the Godhead speaks to the other saying "we" and "our".
peace,
mike