I Would Try A Premium Kitten Food As Smudge Sounds As Though He Needs Some Protein.
Royal Canin Kitten, And Little Kitten Food Are Usually In Specially Marked Bags Making Them A Good Deal.
Bless You For Taking That Older Cat.
You Should See If Theres A Vet College Near You Who Will Help With Smudges Teeth, As The Infection Could Be Dangerous.