well, i am no expert in fact i am just doing my first flasking on commercial media. i am using p668.
well, depends on type of orchids, some may take a couple of months for germination. as long as you do not have bacterial or fungal contamination, all you got to do now is wait.
i notice my p668 media is having those white milky stuff that you mentioned, but so far i dun think it is interfering with the seeds. but i am still waiting for mine to germinate. mine is about near to two months old.
good luck and i hope to hear opinion from other experienced member as well