yoshi,

i recently refinished my west river 180 that had the same 'symptoms' you described...a babied boat built over 10 years ago....but never 'refinished'.

in my case, the 'micro cracks' were apparently the varnish finally failing.

when i sanded most of the old varnish off with 180 grit sandpaper and tested it with mineral spirits....the cracks disappeared. the subsequent varnishing job got the same results. the boat restored to 'like new'. i did not do a new skim coat of epoxy.

that said, mike's right. you will find out what it is when you sand it back.

let us know what your result was.

best of luck