Hi, Justiena . . .
I'm sorry to read about all those fish passing!
I do suspect that so many fish being confined in such a small tank - particularly with a maroon clownfish - probably had a lot to do with it. The angel's "jagged" fins could be due to aggression, or could have been damaged post-mortem. (As mentioned above, that variety of clownfish will get rather too large for a 14 gallon tank all by itself, and it might be a better choice to rehome that one and choose fish - less of them - that will stay smaller. Maybe something like a smaller shrimp-goby, a tailspot blenny and a possum wrasse - that'd be about as much as I'd dare try in a 14, and each of those fish will utilize your tank's landscape in a different way.)
Your "bugs" look like munnid isopods, a cousin of amphipods - and of the roly-polies in your garden. They're harmless scavengers, and an awful lot of fish regard them as tasty snacks. They probably came in on your liverock, and they've got no guilt in the loss of your fish.
You mentioned that your clownfish was less playful today - does he seem actually ill, or is it perhaps because he doesn't have other fish around him? Is he showing any symptoms like swimming into the flow of a powerhead? Hiding from the lights? Head-shaking? "Flashing", scraping some part of his body against rock or sand? Small white specks on his fins or skin?
Hovering near the heater seems pretty normal for clowns - my ocellaris pair sleep next to mine every night, and the way they wiggle around it, I expect them to start laying eggs on it almost any day now.
I'd like to see if we can get some more helpful eyes on your situation, so ... #reefsquad . . .
~Bruce