Based on your description of the second one, the only thing I can think of is Sunnyside Daycare Classmates. It has multiple couples, but only part of it takes place in the ship, but it is definitely intense and kind of gross. The MC wasn't weak tho so I doubt it's this one. If you figure it out, I would be interested in seeing what it was.
https://www.mangago.me/read-manga/sun_kindergarten_classmates/

Hey all!! Im looking for two different bl and I cant find them anywhere -- also, it dont remember the plot for either of these which is making it even harder ;(
1.) Its a manga where the mc's have animal characteristics (i think one ml was a leopard and the other was blonde -- i dont remember if the mc had animal characteristics) and there are two love interests and they end up in a throuple relationship. I think the cover is them all in bed together, but I might be wrong.
2.) This one follows a handful of couples on a spaceship (it might be a prison?) And I remember it being really intense and kind of gross. The Mc was always getting beat up because he was weak or somthing -- I honestly cant remember.
Sorry for the long post -- any help would be appreciated!