Your temp and humidity sound good, and only water them when the cups feel light and at least the first inch or so of soil is bone dry.

Eventually your cups will dry out faster and faster, at which point you should transplant.



Go easy on the Cal-Mag, they wont be taking up too much of it yet.

Make sure not to overwater, the key is to dry 'em out without wilting them.
This makes them grow fastest.

This is just my opinion.

Good luck :stoned: