spots on leaves?

hi all, i have searched everywhere for this problem but cant pin it down to a specific problem.

this is my bonsai bubblegum mother which is about 5-6 weeks old in a 70:30 mix of general purpose potting soil and perlite under 2x 24w 2700k and 2x 24w 6500k cfls at 18/6 in my pc grow case. temps are generally around the 22c mark at all times, dipping to about 18c with lights off.
the other day i noticed a few of these dark spots developing in the middle of a few lower leaves and over the last couple of days it has progressed a lot.
i suspect either a deficiency of manganese, phosphorus or potassium just by looking at the deficiency charts but its hard to tell with those charts.

could anyone point me in the right direction? would be greatly appreciated

thanks for looking!

Been a while, still having this spot problem.
also having this problem on a 3 week old clone in perlite hempy.


Anyone got any ideas?

Anymore information needed?