Has anyone got any idea what may cause loss of brake fluid with the following symptoms.

Renault Scenic, inherited from late father. Car is just over 1 year old, shortly after we got it, noticed the brake fluid light flickering occasionally. Topped up with brake fluid to just below Max and all ok.4 weeks later same thing, resevoir just below Min.

Car has disks all round, there is no loss of braking ability or spongyness, so it doesn't feel as though air is being sucked in.

Plan to book it into the dealer, but is there a rational explanation.

Car is yet to have first service as Renault intervals are two years.