About 6 weeks ago Crusty died, I was upset but he was a very old boy so I wasnt shocked. Then last night I put their toilet roll tubes and hay/food in and Lisa didnt come out to see me, she had been fine when she played out yesterday, the only thing I noticed was her eye looked very slightly swollen, nothing worrying though and I was going to just keep an eye on it. So when she didnt come out I think she must have been already dead, when her toilet roll tubes werent touched I had to destroy her little tunnel system to find her, she was right in the middle curled up . Lisa was only 28 months old so middle aged for a gerbil, I think she must have had the same condition that her sister Maggie died from . I hope this isnt a hereditary condition as Flanders and Millhouse are their brother and father.