Suggest Treatment For Running Nose, Sneezing And Cough

I have several cats one by one their getting sick runny clear nose discharge sneezing coughing also discharge from eyes pus like. Can you tell me what it could be? My husband and I have a stray cat problem our home is a great place to drop them the shelter won t take them so we get them fixed but must take them back. We spend 400 a month in food etc we can t afford to take them all to get the cost so could you recommend something natural or over the counter for them