I have a 20 gallon high with some platies, neon tetras, danios,Corry's,Guppies,shrimp,khulis, and one hillstream loach these last couple of days ive found 2 dead platies a couple more look like they aren't gonna make till tomorrow any idea what could be wrong? i do 50-75 percent water change weekly haven't had a chance to test my water as i ran out of test strips recently