Since the regulator is having zero effect you may want to check that the hairspring is sitting between the regulator pins and not on the outside. If it is then check that the pin gap (space between the pins) isn’t too wide. Under high magnification and while the balance is oscillating, make sure that the spring is vibrating between both pins and is moving all the way across the gap and making contact with each pin. If it’s not hitting the pins or is hitting only one then you’ll have timing problems. One minute in 4 hours is pushing the limit for a regulator problem. I think somewhere around 5 mins per day is as much adjustment as you can get but I could be wrong so checking the hairspring position is worth a try. Also you might check that the hairspring is flat and not tilted off the plane of the balance and/or dragging on the balance arm or making contact with anything else. If it’s losing at a steady rate such as 1 minute in four hours and losing 30 secs in 2 hours or 15 secs in one hour (might want to check that) then diminishing power probably isn’t the problem. If it’s losing most of that 1 minute in the last hour or so then loss of power might be the culprit.
After checking the hairspring please let us know what you find out Jim,