I think the brown one needs some serious attention. You say he's acting tired, which means that he's fading. Rehydration is really really important for this. Syringe feed him some pedialyte if he'll take it. If he won't take any oral liquids, he needs sub-cutaneous fluids, which either you have to know how to do or take to a vet.
Tired=lethargic, which can mean toxins are taking over his body, or not enough water or sugar to survive.
The diarrhea is also a bad sign. Bunnies at this age have really unstable gut bacteria and when they get out of balance, they get diarrhea. Diarrhea is bad for 2 reasons: it's caused by overgrowth of bad bacteria in the intestines, and these bacteria release toxins into the body that can kill a bunny. Diarrhea is also very dehydrating.
If it's truly diarrhea, that combined with the lethargy makes me think he needs to go to the vet ASAP. If that's not possible, pedialyte, hay, and KMR are all he should be getting--no pellets or other sugary stuff. Lots of pedialyte should be given, like 20mL or more.