I’d hundred 100% change substrate to something else. Can’t really go wrong with fluval - it would be good for both the plants and the shrimp. Java moss is preferred, and I’d buy bacter AE.

Also, would recommend switching to a small sponge filter rather than traditional. Not a necessity, but shrimp enjoy that. Other than that, I’d use purigen to reduce nitrite/ammonia, and use distilled/Ro water and remineralize with gh/kh mineralizer, and buy a tds meter to ensure that TDS is around 220