Update: I took your advice WaterGardener and gave the pond a 1 week hiatus from introducing any other meds. The fish didn't improve any and were continuing to suffer. After that week, I gave the pond a treatment of Proform C. After the 2nd dose of Proform C, I did notice about half of the fish improved dramatically. After the 2nd dose, I gave the pond another one-week "break" and performed a 30% water change.
Last week, I used a dose of Dimlin X. Now, the all the fish seem to be perfectly healthy, are swimming around and eating profusely. On many of them, I've even noticed their colors are really starting to brighten up. I think the Dimlin X did the trick. Based off my observations and the fish's behavior, I believe that there were multiple afflictions affecting my fish. Some definitely showed signs of anchor worm, flukes or fish lice while others showed signs of potential fungus infections and ich.
Unfortunately, I'm not surprised as the holding tank conditions the fish were in prior to my purchase were not good at all. I could easily see how all of these diseases and or parasites could easily spread from fish to fish there.
Out of the 18 fish I purchased, 5 of them didn't make it through this ordeal. These were all 4 to 6 inch fish. I also lost 3 of the 1.5 inch fish I already had in the pond from last year.
Some lessons learned that I'd like to pass on to newbees like myself:
1) Don't buy fish in bulk unless you can inspect each and every one of them
2) Don't buy any fish if the conditions they are currently in are not optimal
3) Do research first! Find a reputable dealer or breeder and buy from them. It may cost more upfront, but you'll probably avoid all the issues I had to deal with.
