Hi, with both the second betta and sae it could be dropsy, I have just lost my 4th SAE to this this year. For the first fighter it could be old age, could have had a stroke. Dropsy is caused in theory by the internal organs failing causing the fish to retain fluid, however I think there is a link between this and the amount of bloodworms fed (and I did say 'I think" as others may disagree).