LONG TERM
Your plans to buy a vaccuum bag resealer and a batch drying oven sound good as you say, but you�re correct. They will not help with this current situation.
SHORT TERM
If your connections are clean, free of pits and holes with a smooth, slightly concave, feathered fillet; I would not mess with the BGA that are soldered to the boards. They are fine. The definite line on the balls is demarcation of the extent of the flow of the flux contained in your paste.
Listen. If your BGA are soldering with good flow, do not mess with the balls on the components that are not soldered to boards. These balls are just heavily oxidized. Contact your supplier, if you want confirmation. If you are getting good flow with your current flux: say �pfew�, sign-off on the noncompliance report, and move on to other things.
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