Well, day before yesterday I dosed my aquarium with the first dose of excel, which recommends 5ml per 10 gallons for the first dose or after a big water change. Then it recommends 5ml per 60 gallons daily or every other day. I don't think I will ever add the high dose again because I lost a bolivian ram and a cory the day after I did a water change and added the big dose of excel.
Water parameters are excellent. Ammonia- 0, Nitrite-0, Nitrate barely at 5-10ppm. (I had just done a water change, they were at 10-20ppm before the water change).
So my only thought is that, well sometimes I know fish die for no reason, but also perhaps the high dose of excel could've exacerbated an underlying condition. I do have hard water which has a relatively higher PH (7.6-7.8). The other fish all seem active and happy, but I am sad about the fish that I lost