The only causes I can think of are the usual suspects: Uprooting the substrate without doing a water change afterwards, excessively high fish loads and NH4. If you're innocent of the first two then try to figure where the third might have come from (dead fish unaccounted for, unplugged filter causing bacteria die off, over-cleaning of filter media etc. etc. etc.)
Theoretically, unfit or non-growing leaves have a higher probability of leaching NH4 and nutrients back into the water and are the most likely attach points for the algae. Slower growing plants are the next most likely targets.
Micronutrients? You didn't mention the dosing but presumably you dose if you're basing your scheme on James'.
You shouldn't need to dose more than the recommended levels suggested by EI. The appearance of staghorn is often a sign of over feeding, dirty substrate, etc and also some filamentous green algaes appear due to ammonia spikes that are undetectable by test kits. Whenever doing work on the tank that involves disturbance of the substrate it is a very good idea to do a large water change. CO2 is another cause of these algaes, but it seems as though your levels are good. Have you got good water circulation around all the plants?
It sounds as though it is most likely due to substrate disturbance and/or overfeeding then. Pulling up plants, etc often causes ammonia to be released from the substrate as does over feeding and an unnoticed dead fish/shrimp. Follow any rescaping with a large water change. Let us know how you get on.