Shrimp dying... Nitrate poisoning or lack of sufficient bacteria both as a food source or filtration. Shrimp tanks generally can get by on biological filtration alone however active substrate requires additional finesse due to leeching underwater. The best approach is to plant densely, as weber mentions while preforming water changes.
The dusting is due to lack of mechanical filtration. Biological sponge filters only deal with the chemistry and not the debris and inevitable deters buildup.
There appears to be a slight green haze around the glass so I suspect algae building up.
If you have medium light running for extended durations, algae will usually show this. The additional light is forcing your plants to grow faster towards the light. If there is insufficient nutrients, the the leaves will likely show deficiencies by yellowing, fraying or develop holes.
Shrimpers always quote gh, kh, and ph first and foremost as these are vital parameters to determine whether the tank is suitable for specific breeds. Ammonia, nitrates and nitrides are quoted by general aquarists referring to the overall condition of the tank.
Need the gh and kh and name of the breed kept allow for more specific advice.
If the tank is still leeching and not stabilized yet, I'd recommend several water changes over several days to bring the nitrates down.
I would also add a hob filter and more plants... Like five times more.
My moss grow out tank is a 5 gallon with a 23w 6500k cfl above running 8 hours a day, sometimes three hours more due to me servicing or collecting specimens at night. There is absolutely no algae in the tank and floaters that are covering 1/3 of the tank. If you aren't able to get that sort of plant density immediately, grab a ton of floaters. These guys will be a nice place holder until you do. These guys are the worker plants of planted tanks and will clean and clear your water chemically to soak up nitrates.
I absolutely dose no ferts in the tank but everything that I test plant grows fast and colors up. I dodose this tank with beneficial bacteria and have a healthy colony of prl and pfr working as gardeners.
All in all, your tank is in imbalance. Need to get there and the rest is cake.
"I am Groot", the faithful protector