Hey everyone, havent updated in a long time....well the babies have flourished into flowering beauties, and now comes my next question. WHEN to harvest?

im looking for a nice relaxing stone so im wondering how long i should leave them. HOW do i tell when to chop? I dont have a microscope on any kind so kinda have to just judge by colouring. Here are some pics i took yesterday...

Oh im also wondering should i chop the whole thing at once or should i just pic the ones higher up first....?