I'm a little confused so I'm calling on the bonsai guru's AGAIN !

I have reported a few of my trees into a mix of
60% diatomite 10% zeolite & 30% debco bonsai mix.
In the past I've just used the debco bonsai mix on its own.
Most of the time I use a moisture meter just cause its easier than sticking my finger into every pot,
Problem is even straight after I give the pots an absolute soaking the pots with that mix barely show a reading and never get into the moist zone at all.
It's not even hot at the moment, I'm not going to be able to water every hour on the hour in summer


What have I done wrong ?
Should I be adding more bonsai soil and less diatomite to get it to retain more water or should I add something else ?
My concern is I don't want to be potting any of my maples etc into this mix till I sort it out.
Thanks in advance
Ross