Looking for some assistance with 1 of our Eastern long-necked turtles approximately 2.5 years old. We have two of these bought at the same time, one is perfectly fine the other has been showing signs of puffiness on and off for about a month. Initially it was just the back legs, took the turtle to the local vet, she said eyes are clear, still eating and swimming fine and the puffiness appeared to be trapped air. Vet suggested keeping an eye on this turtle in a separate tank for a while which we did. The turtle seem to be doing OK, we put it back it the main tank, was OK for a while and then started to show signs of puffiness again, this has gradually gotten worse and the puffiness is show front and back. Last two days the turtle has stopped swimming around so much and is not eating as much. Main tank is 3ft long, with a Fluval 306 filter, 90cm UVA/B Globe, dock and heat lamp. Water tested today pH levels 7.4, Ammonia 0ppm, Nitrite 0ppm and nitrate approx 30ppm. The other turtle has shown no signs of illness. Pictures attached, I will be taking the turtle back to the vets tomorrow, but any assistance, advice on what this could be would be very much appreciated.