Hey McD'
.... how cold is it at lights off? The problem with too cold is it jams up nutrient uptake and metabolism, even if there's plenty around... Cold "feet", warmer tops are a bad combo, the busy topside isn't getting what it needs for "supply" below... it takes some hours for the soil/medium to get up to temp.
Do you have anything under the tent for insulation? I use foiled bubble wrap insulation for water heaters as a base/alternately, those 4x2 foil sided styro panels are excellent as well... The bubble wrap could be cut-to-fit inside the tent as well. I know folks may use those seedling heat mats under pots to help as well.
The other hitch is air temp of course, turn over rates and such,... no need for a rapid exchange all the time under such conditions, slow it down if you can so the air in there can warm up...
NMK is a true jungle bitch, this African landrace may not appreciate cool T's much, something else to consider.
If it gets bad, some foliar treatments may help get defc's knocked back some; it's a ball ache in this situation I know, so more judicious applications with a small spray bottle may be called for... Ca-Mg, Si, fulvic is a good mix, half strength; wetting agent a must, as is spraying the undersides of the leaves, more stomata are located there vs. top side, so more gets in...
The advantage here is bypassing the root system, direct injection if you will!