By no means am i an expert with respitory infections but what i would do if i were in that situation is look at my night drops in temp because from what ive gathered these RI's are typically caused by temps dropping below 80 degrees consistently. If your monitor is on a day/night cycle (-temps up in the day, dropping at night)you may want to run day time temps 24/7 and maybe lower the humidity a tad just until the clears up.In my oppinion as long as your monitor is healthy( eating, swimming,basking, hiding, passing feces etc.) and just has a slight sniffle the above methods may clear it up but i'd keep a close eye on it to be sure. If the situation worsens by all means see a vet!!
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Jaye- " When you try of all your forces to make your own way, you will help some of others and will be helped by others. As long as you do not make your own way, you cannot help anybody, and nobody can help you. " (Shunryu Suzuki)