Question sisters/antibiotics

[Janet Morrow]

Hi,   My daughter, seventeen, is keeping two of Hanna's daughters.  The third one we have  not sought a home for as I do not want her to be a solitary gerbil.   The three sisters are now seven weeks old.  This after noon we noticed that all three of them have a slight discharge from the nose.  It looks like old dried blood.  they are eating and drinking fine.  I have not noticed any other symptoms.   We are using aspen wood chips, although the do have a wooden house made out of old pine lumber.   #1.  Should I give them any Tetracycline?  We could only get the fish kind we could find.  It is 250 mg Capsules.    We have been told by Gary that it can be used, but must be changed every day.   #2.  The directions say to use one capsule per 10 NET gallons of aquarium water.  How much would we use for a water bottle, 8 oz. and 4 oz?   #3.  Since the sisters have been together since birth should the make good tank mates?  My daughter is concerned that the 'blood' might be from fighting.   Thank you for your help, Janet and Liz