You’ll need to look at their modding, though (surprise surprise).
Great Mothers: there’s no point in using 3 speed mods and 3 health mods. 2 of the speed mods you have applied (and taken to 6A, inexplicably) have no speed secondary and neither of the non-arrow health mods have any speed secondary either.
Morgan: there’s no point in using 1 speed mod and 1 defence mod. She’d probably be best with protection primary on triangle, circle and cross, but switching out the arrow mod for a defence set arrow would leave her pretty well modded.
Merrin: there’s no point in using 3 potency mods and one tenacity mod. Tenacity is best for her across the board, and there’s no need to use a speed primary arrow or the +20 speed circle mod you’ve got applied.
DTP: other than low or non existent speed secondary stats, this character is modded well.
Night Trooper: there’s no point using one crit chance mod and one tenacity mod. Changing the tenacity mod for a crit chance mod would help. The speed secondary stats are really poor on your current mods. Also need better primary stats on triangle and cross mods (offence / crit damage for triangle, offence for cross).
I know you’ve said you don’t understand modding before, but if you ask and are prepared to follow advice, lots of people would be happy to help you.