There are lots of thing that could go wrong:
1. Over dose of CO2 (DIY CO2 is not ideal) Fish is stronger than shrimp.
2. 6.6 Ph is kind of low for most Neos shrimp
3. Your water parameters
4. Are there other livestock (fishes) in the tank?
5. Temperate is pretty warm, but 77 is not above the norm.
6. Shrimp can die slowly over weeks period when not introduce them properly (acclimating method count)
7. Careful with dosing ferts, it can kill off shrimps.
Edit: Are the Amano shrimps in the tank on your sig? Those are mean fishes, I'm surprise they lasted 2 weeks.
1. Co2 isn't being dosed in excess, ottos are generally the first thing to have problems with co2 and they are fine.
2. I really cant see Ph being the problem with amano shrimp, Ive kept them in more acidic water before
3. Water params are fine, plants and 70% WC's keep it clear.
4. The current stock is 8 rams, 35 rasboras and 7 ottos. (no problems there)
5. I know they prefer cooler water but the rams dont.
6. I acclimated them slowly over a period of hours, I cant see THAT being the issue
7. I tend to underdose with ferts, plus my older amanos have never had problems for months.
8. yes the tank in my sig, Im not sure which fish you are thinking of lol.....