Sounds like the start to a respiratory infection.

What kind of bedding and set up do you have?

You can get some Tetracycline antibiotic powder from the fish section of a petstore. It runs about $13 and comes in packets of 10(500mg each).
Pour one packet into a 16oz water bottle and mix well. Quarantine your male and give him the antibiotic water mix. Change water ever day or every other day for 1-2 weeks. If it's not too advanced, his RI should clear up in 2+ weeks.