Chronic Euvolemic Hyponatremia – Need Se

I am a 47-year-old male with chronic euvolemic hypotonic hyponatremia. One year ago, my sodium dropped to 115 mEq/L while taking Tazloc H (hydrochlorothiazide). It was stopped immediately, but my sodium has remained around 129–130 mEq/L. Latest reports: Sodium 130.1, serum osmolality 259 (low), urine osmolality 118, urine sodium 42, creatinine 0.9 (normal), thyroid normal, 8 AM cortisol 10 (normal range). Symptoms include headaches, brain fog, confusion, and fatigue. My nephrologist suspects Nexito Plus (escitalopram + clonazepam) may be contributing and prescribed fluid restriction and tolvaptan. Does this pattern suggest SIADH? Could Nexito Plus be the cause? Should it be replaced, and are any additional tests recommended? Please help.