that one pic of that leaf is fro ph and or watering.magnesium def. are also,not always wat they apear to be,its usally ph and or watering that mak it look lik a mag,wen its not.somtimes over watering can cuz soil ph to go outa range too.also it cud be ferts. problem.depends on plant size and pot size and with 5 gallon buckets it can be the volume of water ferts mix and or the type and the n-p-k numbers and type of lights,large halides cn handle alot moe ferts.u cud actually do a grow under floresc. n poting soil,with out ferts. if pots big enough and ur not usin a soiless mix.fish emulsions pretty safe,but u can still over dose with it.poting soil and florescent,s just get ur watering right and the amont right for the size of plant and pot size,slam u got it.