Also...pH of 6 or 7 is not acidic. It is near center of the scale, or neutral. Your pH needs to run around 4 after adjusting the brightener level.
Your bath temp needs to run around 125F.
Are your anodes corroded or anode bags filled with gunk?
I could guess on...eg, boric acid content depleted...
But without more specifics about your process it would only be guessing.
If the tanks are small enough, eg a few gallons, it's just as well to start over. The cost of analyzing or guessing will eventually exceed the cost of a few pounds of crystals and some brightener.
You could put the solution aside with a heater boiling off the water till you get down to a level where the solution just starts to thicken. Don't reduce it past this point because it will get messy. Bottle that up and take it to a household hazardous chemicals collection site. If it is a few gallons they won't mind.
Ken
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