re: Growth has stopped

Dave has plants that stopped doing what they are supposed to ...
I think all indications are that you are starving your plants of Nitrogen.
(Poor substrate, little fish food, stopped growth, algae starting). I suggest
that you do do one or all of the following:
a) add dried clay balls to your substrate, with our without added fertilizer;
b) add fertilizer tablets to the substrate;
c) add PMDD or other liquid fertilizer with N, K and trace elements, but no P
d) feed your fish some more (do this in conjuction with c!, otherwise you will
   accumulate Phosphates and algae) 
a bit at a time). I suggest that you start with 1-2 ml of PMDD for the first
two days, then 3-4 for a two days etc. until your Fe reading is up the
recommended .15ppm. Also consider adding (SMALL amounts) of KNO3 seperately
to fine tune your PMDD. 
BTW, I had a very similar problem - and it can re-occur very quickly if you
don't watch your NO3 (or your plants!) carefully.