Dying over past week. Too noob to know...

Hey everyone, so I'm in wk2 of flower and my amnesia haze ladies are suffering from at least one problem if not more. Sitting in 3g pots of FFOF
Water/feed/water
Started feeding Heavy16 BudA&B once I switched to 12/12
No nutes before the switch. Feeding at 1/4 strength of recommended since I've read that heavy 16 is extremely salty. I do not have a ph or ec pen to test. Using tap water during feeding and watering.
Haven't seen any bugs for the most part. A few gnats in the soil during early veg. I sprayed the soil and plants with a mild commercial insecticide and that seemed to get rid of them. So I haven't seen any bugs, even with a loupe, including under the leaves. By far doesn't mean there aren't any since this is my first grow. Any and all help is appreciated! Thanks!

Your plant is over fed so stop using those nutes for a bit. It wouldn't hurt to give the a little more cal/mag.

Check your tap water aswell it could be full of chlorine\chlorimine are you letting it sit atleast over night?

Ahh. Forgot about the tap water/chlorine. And I do think that the nutes shocked the plant, maybe it locked some of the nutes up? Not sure. I filtered some water and I'm going to let it stand overnight and flush 20% in the morning.
Any other suggestions?

1,2,4 could be a phosphorus deficiency
7 could be a manganese deficiency
but its hard to tell from just looking at pics and the solution is all the same just flush your pots a deficiency dosent mean the nutes are not available it just means your plant is not absorbing them properly

do your plants stalks have red/purple lines on them

So after returning for my first half-strength feeding after flushing several times, I think I found the culprit --- the syringe I was using to measure out the nutes. I thought I was measuring cc's, or mL... It was in tsp! So the first feeding which should have been half strength and the two feelings after that were actually like 2x strength. FML...
So I believe what happened is I caused a nute lockup and created a cal/mag def after the initial nute burn. On the brighter side, the tops have recovered and I see trichomes forming again. Lower half has permanent damage but hopefully I can get at least a little yield from the girls. Better late than never, live and learn right? Thx for all the help!