As Camimom said, it's time for a vet.
It's important to note that increasing humidity is not a cure for the respiratory infection, though it may help to thin the mucus so the cham can expel it while the infection itself is treated with an antibiotic.
When a cham has a respiratory infection, as evidenced by a bunch of bubbly mucus, there is little time to waste in getting the cham onto medication.
The longer you wait, the weaker the cham becomes and the stronger the infection gets.