Help with kitty diet - health issues

[MissPurryJess]

I love this forum, and I browse and lurk frequently. I have a few questions about my kitties' diet in relation to health issues, and while I've found some amazing information on the boards, I was hoping the experts could help me with a specific situation.

I'll try to be as succinct as possible! I have 2 kitties, a boy and a girl, Fitzy and Daisy, they're littermates and about 6.5 years old (they're rescues). They each weigh about 9 lbs., so they're at a good weight and don't seem to overeat.

Until the grain recall, I was completely ignorant regarding what my babies needed. :sad: They had been on Science Diet Z/D Dry, and then we switched foods - we tried a few different types of foods (Innova Evo dry, Innova Evo wet, Wellness wet, Natural Balance wet), but finally settled on 1/6 of a can of Innova Evo 95% Duck (per each cat) twice a day with a pinch of psyllium mixed in and Now! Grain-Free Senior/Weight Management Formula dry whenever they want it (we leave a little bit in their bowls all day).

Here's the problem: Daisy Mae has hard stools, and Fitzy has a tendency to vomit. Fitzy used to have loose stools, but since he's been eating the Innova Evo 95% Duck, his stools have been well-formed. His issue is that he eats too much at once and then pukes it all up! We clean up piles of kibble vomit at least once a week - this week he's vomited 3 times (twice kibble, once bile). He also does this horrible hacking thing - the "I need to puke up a hairball but I'm not going to yet" kinda hacking. I freaked out and thought he may have lung cancer or something, but the vet said he was in great health and his lungs sounded good, and suggested giving him Laxatone (which he abhors and we have to put it in a syringe and force feed it to him), but I haven't seen a marked improvement yet. He hasn't hacked up any huge hairballs lately, but there has been some hair in his vomit. I'm so worried about him - I was hoping you guys would have insight on that. He's always had a sensitive tummy - he vomited a lot as a baby, so this isn't a new thing.

And then there's Daisy Mae - she has hard stools! Which is why we tried the Now! dry food - the nutritionist told us it was high in fiber and low in fat, and that it should help her. No dice. That's also why we give them psyllium powder - the vet thought it may help with her stools, but I don't really think that's working, either.

Otherwise my babies are in good health, their fur is nice and shiny and there's no dandruff or allergies or anything, just the vomiting and hard stools that I'm worried about. Please help me - I love my babies more than anything in the world and I want to make sure they're as healthy and happy as possible. Any insight or advice is greatly appreciated!

Whew, I'm verbose.