I would not consider the described behaviours as normal. I think it much more likely it was due to severe stress, and the subsequent fish deaths bear this out.
As was mentioned, the named fish need groups, they are shoaling fish by nature and live in large groups. The "silver sharks" are presumably the Bala Shark
[click the shaded name for the profile with photos]; common names are next to useless and can be very confusing, so correct me if this is an erroneous assumption. But if it is correct, this species needs a group of 8 and a very large tank. Please read the profile. The 29g tank [30-inch length was mentioned, so another assumption this is a 29g tank] is not sufficient for this species.
When shoaling fish are not in a sufficient-sized group, they can become highly stressed. Shoaling fish have evolved to be in groups for a reason, and their health and lifespan is directly related. Stress causes a weakening of the immune system at the least, and further problems and early demise almost always follow.
Same applies to the Clown Loach
; loaches are highly social fish, and a group of five is minimum, but this fish grows too and needs a 6+ foot tank. Please read its profile.
I get the impression this was a fairly new setup, a week of these fish being together was mentioned, so undoubtedly the "cycling" came into play too, adding further stress.
You can read about the harm of stress here: Stress and Freshwater Aquarium Fish
Some decisions have to be made with respect to the fish left in this tank, hopefully to improve their health.