Record where and when the defect appears
Photograph edges and recesses and note whether the issue followed a change in current, additions, filtration or workload.
Check interacting factors
Review current density, temperature, pH, chemical analysis, filtration and anode condition. A burn does not automatically prove that one additive is low.
Correct with evidence
If pH or bath components are outside the range for the installed process, brightener may not perform correctly. Confirm the basics first, then make a controlled addition based on analysis.
Technical note: Operating ranges and additive doses depend on the installed chemistry, equipment and production load. Use the supplier data sheet, bath analysis and approved safety procedures.