Not about this issue, but about the blue when adding carbonate to the wash.
Sodium Bicarbonate and turning into Sodium Carbonate:
Dissolving and stirring sodium bicarbonate (NaHCO3) in boiling water -> Na2CO3 (Sodium Carbonate) + CO2 (Carbon Dioxide) + H2O (Water)
Sodium Carbonate in the wash with DAP and why it turns to ammonia:
2(NH4)2HPO4 (Diammonium Phosphate) + 3Na2CO3 (Sodium Carbonate) -> 3CO2 (Carbon Dioxide) + 3H2O (Water) + 4NH3 (Ammonia Gas) + 2Na3PO4 (Trisodium Phosphate)
Trisodium Phosphate is a pretty good cleaner though haha.
No idea why it turns blue. A complex set of reactions leading to the formation of Schweizer's reagent?