If the lion has been eating daily, first of all that's WAY too much to be feeding it. Lionfishes are binge/fast predators, and have very slow metabolisms. If too much food is offered, it can kill them, as they can become impacted, or in some cases, the food can actually begin to decompose in their GI tract, which generally kills them. A healthy lionfish can go a month without eating before it begins to loose a lot of muscle mass, so i wouldn't worry about feeding it.
Also, sticking food right in its face isn't a good method of target feeding it (try putting your hand on your nose and see how well you can see it). BTW, lions don't hunt by scent...it's all vision and motion. The best way to feed it is to use a "stealth stick" and let the fish see the food from a distance, and "tease" it by moving the food towards them and away from them.
Krill in any form isn't healthy for the fish when used exclusively, and freeze-dried krill tends to get fishes "hooked" on it (in some circles, it's known as "fish crack"). This makes it hard to get the fish eating anything else. Additionally, a diet high in krill in any form has been linked to lockjaw in predatory species. We believe that this is due to the inordinate amount of fluoride in the shell, coupled with the lack of vitamins B1 and C, which can result in mandibular deformation as the fish grows.
The lion might be flaring its gills at its tankmates, but it also might have gill flukes or ******. Until you figure this out, I'd increase the aeration in the tank with an airline or by adjusting the surface turbulence using a powerhead.
You said the lion's eyes aren't "popped", but are they cloudy?
What species of lion do you have?
How long have you had it?
What temp are you running?
Has the fish shed its cuticle recently, or has it been shedding a lot?
Have you made any changes to the system recently (new fish, equipment, etc)?
Most importantly post a few good photos of the lionfish. Experienced eyes might see something you're missing.