Two dead fish within 3 days

Hi there, I am brand new to this forum and very happy to have found you guys. So I have two tanks. One for goldfish variety and one for small tropicals. The tropical fish are in a 20 gallon for about 1 1/2 years now and will be moved to either a 40 or 75 gallon at the end of November when we return from a trip. Two of the fish that I have had from the beginning, one white guppy and one orange and white small sword tail died within days of one another. I was shocked since I have had them and a couple of others the longest. Both of them had both eyes, it appears, plucked out of the sockets. I have read different things about why this happens. It could be bacterial, bullying or after they die for any reason, other fish eat the eyes first since they are exposed. I test my water on a regular basis and at this time, it seems healthier than other times. The water has been awful several times in the past and no deaths, at least not like this. Please help me, as I do not want to lose anymore. It is 5:30pm here in NOLA and I am just about to test the water again. I did a 40% water change yesterday. I will come back on with the results shortly. Thank you so much
Attached are images of both fish.The white molly was Saturday Oct. 28 and the white/orange was today.

Hello sorry about your losses, looks most distressing! What other fish do you have in the tank?

Hello Mother. I've been in the water keeping hobby for a while and have noticed that fish deaths are mostly water related. I've found if I keep up on my water changes, my fish stay healthy. I always change half the tank water every week. I don't keep tanks smaller than 45 gallons. For me, the water chemistry in small tanks is just too unstable for keeping fish. I've found with small tanks, if you miss a water change or don't change enough water, you can and often do lose fish. Larger tanks leave you a little wiggle room if you make a mistake in tank management. For me, keeping the water clean is the only way to keep my fish in good health. If I do this simple thing, I don't have to wonder if my fish are healthy.

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