Turtlers acting strangely

Question
I have two painted turtle.  One I have had for about 1 1/2 years and is small about 3 inches long.Another one is about 4 inches and i have had him for 6 months. I have two tanks a 75 gallon and 46 and kept them separate. I have the little one with a r.e.s and a cooter and the big one with a snapping turtle and two south American long necks. i recently put the two painted turtles in the 75 gallon for a month when i had a baby snapping turtle and the painted turtle bit the snapping turtles tail. after the baby turtle passed away i put them in there original tanks. the both started to bask for long time and stopped eating. I put the little one back in the 75 gallon tank. Now they both don't eat, they bask all day, when they do swim they float and air bubbles often come out of there mouths.  And lately the little one will crawl on the rock, stretch his neck, and make an odd bubbly noise and bubbles will come out of its mouth.and both of them will open there mouths while basking. Also they used to jump off there rocks when they even thought somebody was entering the room and now the dont even if you are directly over them. Sorry this is so long and if you could respon i would be thankfull.

Answer
They are showing signs of respiratory infection (RI), which can be quite serious and hard to treat, even for vets and experienced keepers.

RI is the equivalent of a bad cold or flu.  The basic care is to ensure that the turtle is getting the right housing, care, and diet, to boost water temps about 5 degrees (from a normal 75-80F to about 80-85F), offering the turtles good real sunlight (not filtered through glass or plastic), and a nutritious diet.

Reviewing the basic cares at a good site like http://www.austinsturtlepage.com is a good start. They also have a good medical care page.

One thing that came to mind while reading this is that we usually recommend not mixing species from different countries together because many turtles carry bugs that they are resistant to, but that can easily affect those from other places and I wonder if that happened here.