Most "veggie" foods also contain fish/shrimp meal which means the fish will more likely eat it, thus also getting their veggies
Stores that carry the Nutrafin line will often have the sinking tabs. May have to call around, or consider online.
On your last post, considering the amount of food (and the same type) you've been feeding, it may take a while to get the corys to eat something new. This is frequent. And one reason I always recommend a variety. Fish have preferences, even naturally, and like I noted, the loaches go bananas over the Nutrafin, more than others, but they do eat the others if not as readily. When I try a new food with any fish, sometimes it can take a while (several feedings) before they actually acquire a taste for it.
One trick I use is with something new, feed it the day following a "fast" day. It is fine to not feed fish one day a week; I always do this on water change days. So the day following they will be not only more hungry, but after the water change probably more active, and thus more likely to try something different. Just as with some kids, you have to coax them with trickery.
Sinking foods can remain in the aquarium for a while, just keep an eye on them. If they start to fungus, siphon them out. Having snails (Malaysian Livebearing in particular, or pond or bladder snails)solves this problem. Any uneaten food is quickly eaten by them.