I also find when feeding bottom dwellers I use a turkey baster. I feed the fish on top first then I use the turkey baster to blast a little down on the bottom.
I do this a lot when I get new cory cats and such. Sometimes they're a little too shy at first to come up. Then I do the turkey baster thing when feeding about once a week or every other week just to give them a little extra down there.
I have the opposite problem! I think my platys are malnourished because my guppies and glofish eat EVERYTHING as soon as it hits the water. My platys hang out in mid-level and will go up once the other fish are done and nothing is there. So, I will try the suggestions of others for my platys! I will be getting corys eventually so the tips will become very helpful if they are even more shy than the platys!
Maybe you have this food already or maybe it does not suit your fish but just in case this helps, I just purchased a heavy sort of food made for both tropical mid-water fish and bottom dwellers, it falls to the bottom of the tank after a few seconds so maybe it would suit your situation as it covers the whole internal area of the tank. It is called tetra prima mini granules. You might know of it or have it even but I thought I should say it just in case!
I use my fish-turkey-baster every day! You can get one for only a few dollars, but it's really indispensable. I used it last night to feed everyone bloodworms - suck up a few, then spot feed single fish (two bettas and an apisto) or sprinkle all over the surface so everyone gets some (community tank). I also use it for dosing dry fertilizers (I mix the powder in tank water first).
At any rate, even if you find another solution or find that using e_watson's method doesn't work (which I think it totally should), a turkey baster is a great tool to have anyway so it definitely wouldn't go to waste.
They learn. When I had my apisto (fish in my avatar) in my 55 gallon, he wasn't getting enough food, and I tried to feed him with a baster and he swam away. I eventually started just using the baster to drop the food from like six inches up or so, so it would fall on him but he wouldn't be scared of the baster. Now he swims right up to it. I feed him flakes from my fingers (I hold them right under the water and he grabs them out of my fingers) and I feel him bloodworms from the turkey baster. They learn to associate it with food eventually.