Oh my, there are so many! You made a great choice to go to Balos out of season, in August there are hundreds of people there, not so perfect. My favourite trip to Balos was 1 sunny January day, where we saw not a soul from leaving Kissamos.
Out of season, obviously Elafonisi (but not near the carpark; walk/wade across the lagoon & over the sanddunes to find the perfect, pink tinged beach. Or Kedrodasos, next to it, please do be careful not to touch the juniper trees, they are very endangered.
The beaches at Falasarna are great, there are around 5, each with a slightly different feel, from the well-named Big Beach, up to the (my fave) Orange & Blue beach at the northern end. Whilst there, a little visit to the ancient port is worth it, to see where the ancient harbour wall has risen several metres.
Lots of great, quiet beaches on the South-West coast - the village of Sougia. Next to Frangokastelli (again the main beach is busy in summer now). Sweetwater & Marmara near Loutro. My favourites, because the water is clear, lovely scenery & there are few facilities & few people, are Agia Fotia, Ligres & Triopetra, all very quiet, south of Spili (S Rethymno prefecture).
