Edmond swept to a runaway victory in the men's 200 metres breaststroke and then Marshall came through with a blistering finish to take the gold in the women's 200 metres freestyle.
Edmond clocked 2:05.63 to beat the European short-course record of 2:06.95 set by Austria's Maxim Podoprigora in Berlin on January 25 this year.
Andrew Bree, roared on by the home crowd, brought Ireland their first medal of the championships when he came through for the silver in 2:08.02. Dutchman Thijs van Valkengoed won bronze in 2:08.30.
VDH steers Dutch to relay world record
Defending champion Alena Popchanka of Belarus, the world long-course title-holder, took the women's 200 freestyle out at a breakneck pace inside world record schedule for the first half of the race.
But she could not sustain it and Marshall burst through in the final 50 metres to win in 1:55.10. Josefin Lillhage of Sweden came through for the silver in 1:55.57, leaving Popchanka with the bronze in 1:55.66.
Hungary's Eva Risztov, who retained her 200 metres butterfly crown on Thursday, won her second title with a clearcut victory in the 400 individual medley, ahead of Russia's Yana Tolkacheva and Teresa Rohmann of Germany.
Defending champion Peter Mankoc of Slovenia and Finland's Jani Sievinen, who retained his 200 individual medley title on Thursday, shared victory in the men's 100 metres individual medley in a dead-heat in 53.35 seconds.
VDH looking to finish in style
VDH flirts with 100m freestyle world record