Swift great at first now have problems

I have been using CPAP for the last two months. I started with a Resmed Autoset 8 and a Resmed Quattro full face mask. I have been experimenting over the last month with different masks to try to find something more comfortable. I tried the Resmed Swift several weeks ago and for the first week it was amazing. Extremely comfortable (like nothing is on my face), great results shown on the Autoset the next morning, few leaks, and great energy.

Now over the last week I can't stop from opening my lips and leaking air. The max pressure the S8 shows is 9.4 but that is similar to what it was showing the first week. I've tried a chin strap but that doesn't work because it only keeps my jaw up and my mouth closed. My lips can still pop open with it. I can't understand what happened. It's almost as if the pressure put through my airway is too much and it's forcing air to push open my lips. Again, this never happened the first week. I am really perplexed. Any ideas out there?

Also, could the mask setting on the Autoset have anything to do with this? I woke up this morning (another bad night with the swift) and found that I had accidentally left the machine set to "Mirage Full" instead of "Swift". Could this have any effect? Does anybody know what the machine does differently when you change the mask setting on it?

I believe the mask setting has to do with the leak calculation. The expected leak from your full face mask would be higher than from the Swift - so reported leak would be off.

You might try adjusting the humidty settings - sometimes more or less humidty will cause some congestion and opening your mouth to breathe.

The above is my post. I posted before I logged in so it posted as a guest. I apologize for posting before searching the forum. I have found several answers for the "blowfish" problem on various threads but I'm still not sure why it didn't happen the first week and it is now. Any thoughts? Also do any tapers have any concern about what would happen if their nose got stuffy in the night when their mouth is taped shut? I use an Autoset so I suppose it would just drive more air pressure through my nose and keep me from suffocating.

For anyone out there who finds nasal pillows feel suffocating at first, there are three solutions. One is set set the starting pressure higher if your machine allows you to do that (My starting pressure was 6 with a Quattro and I had to change to 8 on the Swift). Second, is to turn off settling or ramping so the pressure is max at onset and third is to enable EPR (or the equivalent on the Resironics machines, if you have a CPAP macine with expiratory relief) so you don't have to exhale so hard to get the air out through your nose.

Thanks for explaining the mask settings!