Can you describe "flu"?
There are some approved poultry remedies, but they may require withdrawal periods for egg consumption, and the problem may still be dormant within your flock i.e. if you add new birds them may contract it or if your birds are rehomed they may affect the new flock.
UC Davis Extension may have some information to share if you would like contact info.
the 2 silkie nostrils or completely congested "thick snot" they have to breath from their mouth one is really struggling ,both their eyes are puffy and the hamshire is walking around slow and clumsy doesn't eat much she will find a place in the morning sit half the day ,then find herself a new spot and sit there the rest of the day. ive been giving them vitamins because they don't eat much