Mouth breathing?

Last night was the first I really noticed this. I woke up several times with my mouth open and air rushing out. I have some ideas on the cause. I switched from auto to straight CPAP at my prescribed pressure (12). This is a bit higher than the 90% pressure the machine has reported, so I'm sleeping with a slightly higher pressure than I am used to. Also, I'm starting to have allergy problems (early spring is always bad for me), and I may have been congested. I also felt like the C-Flex didn't provide as much exhalation relief as the A-Flex, but I can only use C-Flex in CPAP mode.

I'm going to try a decongestant before bed tonight to see if that helps. Hopefully I'll get used to the higher pressure quickly, too. If not, I may have to go to a full-face mask or a chin strap.