Have you got a test kit to check ammonia, nitrites etc? Do you know if your tank has cycled? If not, you want to start there. Otherwise they might all die from poisoned water conditions.
Also, those neons are going to be living (if they are still living) in a state of terror, so you need to do something for them. They will be stressed anyway without a shoal to be in- and they are in a tank with big neon-eating predators! You need to decide to find a new home for someone here- either the big hunters or the little shrinking violets. You have a good-sized tanks so keeping one of those sharks (or so) shouldn't be a problem, but then they need robust tank mates- you can't keep everything you've got at the moment. OR you can take back all the big bullies and stock up on smaller shoalers (once the cycling is done). Guppies with their long tails cannot be in with anything fin-nipping (or fish-eating). Good basic rule is, never buy anything until you have checked (in books, online, on this forum!) what its needs are and what it goes with. It is easy to blame the lfs, but they often have a difficult situation with untrained staff and a very natural urge to make money.
It is a bit of a steep learning curve, this fishkeeping lark, but I'm sure it will work out.