Benadryl is an allergy medication so may not do as much for them as another med might.
It sounds like your new dog might have brought in either kennel cough
www.marvistavet.com/html/body_kennel_cough.html
or canine influenza
www.marvistavet.com/html/body_canine_influenza.html
Both of these are very easily picked up from another dog particularly in a stressful shelter situation.
You can see if some Robitussin DM will help the dogs breathe better and control any cough or sneezing or runny nose. Read here about cautions and dose info
http://www.petplace.com/drug-library/dextromethorphan-robitussin-dm/page1.aspx
You may find that bringing up the humidity in your home helps with breathing. Bringing a really congested dog into a steamy bathroom can help break up congestion too.
You can see and hear a dog with kennel cough here
http://www.youtube.com/watch?v=amGKQX9zdug&feature=related
http://www.youtube.com/watch?v=uN3RpoU0qXw
If you are seeiing a colored discharge from nose or eyes, if any of your dogs coughs stuff up, seems lethargic, has any real trouble with breathing, or goes off eating, see your vet with that one as that dog may have a secondary bacterial infection, including potentially deadly pneumonia, that will need antibiotics or other meds.
As cash flow is an issue, check with your local humane society to see if there is local low cost vet care, ask your vet if you can do time payments or here are some groups that might help you afford the vet bills:American Animal Hospital Associationhttp://www.aahahelpingpets.org/" Through the AAHA Helping Pets Fund, veterinary care is possible for sick or injured pets even if they have been abandoned or if their owner is experiencing financial hardship."Angels 4 Animalshttp://www.angels4animals.org/"Our services range from financial aid to complete treatmentto those pets and pet owners in need."Care Credit If you qualify this may work well for you.http://www.carecredit.com/A credit card company for health care, including veterinary care."With a comprehensive range of plan options, fortreatment or procedure fees from $1 to over $25,000, we offer a planand a low monthly payment to fit comfortably into almost everybudget." They have a zero interest program if you pay within a certain time frame and they list the vets who work with their product.God's Creatures Ministryhttp://www.all-creatures.org/gcm/help-cf.html"This fund helps pay for veterinarian bills for those who need help."Help-A-Pethttp://www.help-a-pet.org/home.html http://www.help-a-pet.org/"Our efforts focus on serving the elderly, the disabled, and theworking poor."IMOMhttp://www.imom.org/"We are dedicated to insure that nocompanion animal has to be euthanized simply because their caretakeris financially challenged."The Pet Fundhttp://thepetfund.com/"The Pet Fund is a registered 501(c)3 nonprofit association thatprovides financial assistance to owners of domestic animals who needurgent veterinary care."United Animal Nationshttp://www.uan.org/lifeline/index.html"The m ission of LifeLine is to help homeless or recently rescuedanimals suffering from life-threatening conditions that requirespecific and immediate emergency veterinary care. We strive to serveGood Samaritans and rescue groups who take in sick or injuredanimals. In certain cases, LifeLine can also assist senior citizensand low-income families pay for immediate emergency veterinary care." They also keep a list of local and national help resources herehttp://www.uan.org/index.cfm?navid=163
More groups here http://www.speakingforspot.com/helppayingforveterinarycare.html
Hope this helps you!
Dog Expert:Rescue, Train,Breed,Care
30+ yrs dog home vet care & nursing, rescue, behavior&training, responsible show breeding, genetics