Blood Parrots are really shy when they are young and and sometimes as adults.
1. Adding decor can help sometimes
2. Making sure you water parameters are fine: Ammonia 0, Nitrite 0, Nitrate 0-40, Temp 80-84F (26-29C).
3. Adding more nonaggressive fish to the tank
4. Give them some time
I would advise against adding Koi and Cobalt Blues. Koi are cold water fish where all your other fish are tropical. They also very dirty fish. Cobalt Blue are African Cichlid which have different water requirements and generally are advised against mixing with American Cichlids (Discus and Parrots). Discus are also shy fish that require pristine water conditions so adding Koi will stress it out badly and so could adding the Cobalt Blues. I would suggest adding some small nonagressive cichlids or possibly some larger body tetras like Bleeding Hearts if you want to add something.