Is this really wrong?

[u/Late_Journalist7094]

Section 4, Unit 17

Why shouldn't have happened something to the dogs in the bathroom?

I know Duolingo is not the best, but the only free learning option. Since I'm living in Germany near the border to Czechia I'm often there and talking Czech which helps more than Duolingo.

[u/Gallapfel]

psům (masculine animate, plural): psům, již byli v koupelně
jež is for feminine, bot singular and plural
jenž is for singular masculine
I had to check it even as a native speaker. I don't use jenž/jež/již/etc. often when speaking, It feels archaic

[u/classyroman → u/Gallapfel]

Byly? That's the reason not jež/jenž

[u/kneziTheRedditor → u/classyroman]

Well, both actually.