They will be fine for now i would get better filtration and do 2 35% water changes a week. i had 3 in a 125g with the right filtration and water changes it will be fine
how often do you change water cause thats way more important than filtration? and you have plenty of filtration if you change enough water. 50% twice a week and youll be fine 20% once a week and youll have some unhealthy fish
i'd feel bad keeping even the two in a 125, some people keep them in 75g and I find it sad, i've seen monster oscars, and keeping them in anything but a 180 as a group or 125 single is depressing, however if it works for you now I wouldn't add another.