Damn this shit blew up out of left field!
My 2 cents- if you're not watering for weeks on end, and your plants aren't thirsty, your moisture retention is all fucked up.
You either need better drainage, ie perlite, or need to add something that doesn't hold so much moisture. Usually perlite will do the trick but you may need to add a fuck ton, which is ok because the soil is to dense.
Think about it; your soil is too dense so the roots can't grow well, the drainage sucks because of it, and it holds too much moisture so the plants is drowning for days after you water. If you water with less volume you cage your root system, the roots and the plant suffer. Stunted growth, ph problems, ect.
Plus all the time waiting between waterings means it will be hard to tell when to actually water without dehydrating or drowning your plants. Also all the held moisture leaves you more susceptible to pathogens.
It's seriously not a nutrient issue, unless you count the fact that if you're plants are drowning then they can't properly uptake the nutrients already in the soil let alone ones you're adding.
Seriously, you're already way behind so what do you have to lose? Get better draining soil you're plant will take off and make it worth it. You keep screwing around with nutrients and it's going to take forever and never live close to potential.