I know this sounds weird but, congratulations on your poo Tigger, hope you get rid of the rest soon!  Our cats love Tuna out of a people can too Connie, obviously great kitty minds think alike :)  Mrs. B mentioned that going for a long motorcycle ride helps her in that situation but I don't know if Tigger has a Harley lol.

Have you tried pro-biotic yoghurt to help Tigger with her digestion?  I know there are special ones for cats but our vet reckons that the human ones are OK so long as the cat doesn't have a milk allergy and it isn't used for too long.  Our vet really doesn't like cats to have milk for too long.

All the best to Tigger et al., hugs, thoughts and purrs coming your way.