Me too. I just found mine leaked down over an inch in one day and discovered the air purge valve on the top of my filter was dripping. I lubed the o-ring and cleaned it out and it looks like it stopped. So make sure to check anywhere that looks wet.I find it strange that you would "all of a sudden" have a water loss. Could you have put water to waste when you were trying to vacuum?
Alternatively, if it truly a leak, could you have damaged the vinyl with your brush or net?
Also, one idea is to turn off the valve to the main drain suction and only suck water from the skimmers. See if there is any difference in leak rate. Then do the opposite, open main drain suction and close skimmers. Monitor for any decrease in water level.