So I just washed a batch of BG 4.0 and they came out smelling like a fish tank... I re-washed them... Still smelling the same

I already washed a load of dirty diapers and those came out smelling fine... But now this other load smells gross.
The first load that came out smelling fresh went like this...
Front load HE (kenmore he3t)
Express wash, hot then cold, 2nd rinse, no spin, a half dose of tide powder.
Normal cycle, hot then cold, 2nd rinse, high spin, reg dose of tide (3 tablespoons)
The downside was there was a faint yellow stain on his poopy diapers (EBF).
To hopefully avoid the stain I tweaked the cycle after some advice. I switched to cold/cold for the initial express wash. I also didn't use any tide for this first part because someone mentioned buildup concerns.
I'm assuming I should just go back to what I did the first time? Will the fish smell go away if I wash them again?
Re: Fish smell after 1 use :(