Glad to hear about Mandarin eating the lysine treats!

Purina Naturals is not grain free. It has 2 forms of corn and wheat, as well as soy - while not a grain it is often a source of intolerances in cats.
Go to the nutrition forum and ask about dry grain free. I do give my boys some grain eventhough there is suspected FHV in my household as well as irritable bowel - b/c of urinary Ph. So tricky to sort all this out but I found a combo that works.
Some of the grain frees are too rich and need to be mixed with a little high quality grained food. So you just try to strike the right balance.
I feed Taste of the Wild Feline dry and combine Authority, Nutro and certain Fancy Feast wets ( classic pate's do not have grain in them. read labels carefully.)
It also depends on what is available in your area.
They get grain free treats - I use EVO herring and salmon dry, as well as PureBites freeze dried cooked chicken.