If it's is wasting disease you would want to treat with Expel p active ingredient is levamisole once a week for 4 weeks I don't think it's necessary to treat with the med trio Expel p is safe to use with fry it's also possible it's low kH that's causing the deaths your seeing as lack of minerals can cause a lot of health problems in livebearers hopefully The added crushed coral helps you can also us aragonite to raise your KH and GH @Kim_D