how about some specs.
How long plants have been in tank?
CO2? pressurized, diy?
lighting? (wpg and type)
recent changes to tank?
Tanks size is 6ft 550l (138g)
Plants have been in tank - 6 months for anubia & sword, 2 years for water sprite
Biolad is high - 14 well fed discus & about 30 tetras
Pressurised co2 with controller. ph is set at 6.3, KH is 2.4, about 36ppm. no drop checker
lighting is odno ~2.5 wpg
sump with wet/dry filter (I've put lids on etc & fiddled a lot to reduce turbulence etc to avoid co2 loss)
ferts...dry ferts added at w/c k2so4, mgso4, cacl2, trace mix. Starting to dose more often than just w/c now
w/c's 35% at least once per week
nitrates hover around 20ppm
changes errrr....probably too many to mention - replaced tubes from 6500k shoplights to plant tubes (mix of phillips aquarelle, sylvania aquastar, hagen aquaglo & sylvania grolux), upped co2 (been battling bba), increased ferts, recently dosed azoo bba killer (worked!), just finished blackout for BGA (also worked), removed some boring plants & added some red to tank (rotala macranda etc).
Obviously I already know it's a fert deficiency probably brought on by increased co2 and arguably better lighting. I have already started increasing ferts.
I would love to know which nutrient was lacking and not just be adding ferts blindly though.