Definitely a lot going on there dude, I am not sure you can save it and get a productive harvest with the issues you got going, I didnt know what to look at first. Sometimes you need to weigh out the decision to flip them into flower if plants are sick or have pests while in veg, its wise not to switch them to 12/12 until those problems are non existent or 100% under control and plants are as healthy as they could possibly be. If they are sick when you flip to 12/12, more than likely they arent going to make it to the finish line and if they do you'll wish you didnt waist your time. I'm not one for throwing in the towel either but sometimes you have to weigh out the benefits of keeping a crop alive or starting over, plus to growing indoors but its never a plus chopping down before you are supposed to.
Start by flushing out the containers with 3 times the container size. If your plants are in 1 gallon containers, pour 3 gallons of PHed (6.5ph max) water threw each plant, if you have plants in 5 gallon buckets, 15 gallons of water needs to go through. It sounds like a lot but as long as you are letting them dry out after properly, your plants will reward you in the end. You can also use flushing agents like
clearex, sledgehammer or a million others and not have to use so much water but I would still recommend using some water after the flushing agent.
When I flush with
clearex with a 3 gallon pot, I will put 1 gallon of
clearex threw followed by at least 2 gallons of aerated PHed water. If you use a flushing agent, follow the instructions best you can, most will tell you to pour mix in until you get a certain amount of run off. Stick with what the bottle says or ask about a specific product.
Flushing will accomplish more than just helping with salt build up, it will help you get your PH back in check which I also think is a big part of your problem as ML said above. If your PH is off its going to make you think your plant is deficient of everything, and trying to fix 10 different deficiency's is going to start a larger problem. When PH is out of the proper zone your plant cant eat. Its more detailed than that but in a nutshell, they aint eating and wont until its corrected.
I really dont want to sound like a downer but dont expect soda bottle sized colas, nor should you get your hopes high for a bumper crop, its tough to get them right if you handle all your problems before they enter the flowering room, if you run into these kind of problems while you are already in flower or as I said above, right before you flip them its not going to work out for you. The plant needs to be in tip top condition before you set that timer to 12/12.
I hope it works out for you man, good luck.
