Fish spitting out food + stringy Poop

Hi all,
This is my first post on this forum. I'm new to the hobby and may have made the mistake of ordering fish online. I bought 4 neon green rasboras and 10 rummy nose rasboras. 2 neon greens died within a few days of receiving (1 began swimming upside down and died and the other I found dead). I've also noticed that my rummy nose rasboras all have long stringy (mostly dark) poop and keep spitting out their food. It's been 5 days of this. I tried micro pellets, frozen bloodworms and brine shrimp to no avail. I'm not sure what is happening. When I received the shipment, the bags of water seemed very cold. I also probably made the mistake of tranferring to my display take because I was worried about quarantine tank water parameter stability. I will attach some pictures of what I'm referring to. What should I do?! I currently have kanaplex and ich treatments. Planning on getting API general cure tomorrow.

I'm not sure what to suggest with spitting out food, but there is a good thread on here about the stringy poo, although white, not dark poo, so keep waiting on other responses to your query here https://www.fishforums.net/threads/what-to-do-if-your-fish-has-stringy-white-poop.466276/

Fish have their teeth in the roof of their mouths and in their throats, so spitting out food and pulling it back in again, often many times, is usually chewing. As they rasp off food, or the food softens, they swallow it all. It scares every new aquarist.

Stringy poop is normal, and that looks very healthy. Every experienced fishkeeper turns into a semi-professional poopologist.

The neon green rasbora is usually Microdevario kubotai. I've seen other fish sold with that name, but most are kubotai. They like slightly softer water than your Sawbwa (Asian rummy nose). If your tap water is too soft, the Sawbwa will tell you as their noses won't be red. Those two aren't fish I'd keep together because their needs are different.

Long poop strings (that aren’t white) say to me nothing’s wrong but the fish isn’t digesting the food very well, since most of it is going straight through. I’d maybe try to find a more digestible food for them?

And heed what Gary has said. Sawbwa want hard water, Microdevario want soft water.

I keep Rummynose Rasboras and they always spit out larger flakes as well as pellets and even live foods then re-eat them. I also see them eating from algae wafers I put in for my ottos and amano shrimp. The long stringy poo I've only ever had once or twice but that was white coloured from an ill fish. I once ordered these fish online as well, got 6 and 1 survived but these fish were too small (1.5-2cm) and young to be shipped IMO. It seems your shipment sent good aged fish but yours are quite a pale colour compared to the ones I've seen.
@GaryE explained why