I think the hikari crab cuisine is the go to. I'm right there with you, my amano's don't really care how much they get via food. I've never had issues and when I do try to target feed them, they just.... would rather eat everything than anything specific. I am probably going to need to be more consistent, once a week or something, to give them some calcium.
As long as KH isn't causing issues, PH doesn't crash after 24 hours of Aeration, your PH is above 7.2 or so, you should be "fine". I would simply add more things, even pleco caves, mopani or ghostwood, driftwood, etc.
More surfaces. Maybe one of the co-op planters with some vallisnaria or Anubias or Java Fern? Something with broad leaves the snails can "entertain themselves on".
Keep an eye on pecking, especially on non-feeding hours, and then you'll have to catch them in the act so to speak.
If you can, keep a log of water testing, deaths, anything you're seeing, and then hopefully something sticks out the next few weeks.