Emergency help my plants are dying

Please help out guys what deficiency do i have ? Im just resolving of overwatering problem but all my plants are getting yellow please share your ideas

I think people May need abit more information from you to help you out better.
What medium you’re using
What feed you’re giving them and what strength
Frequency of feeding
Ph you’re using
How old they are.
I mean to me looking like you’ve given them too much nutes but I’m totally new so wait for someone better qualified.

From what i can see in your photos, the growing medium is coco with perlite, i suspect you have not buffered the coco firstly, prior to planting, so they will die unfortunately, because they have a calcium/magnesium deficiency
Firstly you need to remove the fine coco peat from the coco,thoroughly flush the coco through a collander/sive, and let run off go into to a flower bed with a hosepipe,if your going to do it inside rinse over a bucket with a shower attachment do not let run off go down the plug hole/ drain otherwise you will end up with a blocked drain.
Once you have removed all the fine crap from the coco peat, then i get a 30ltr bucket fill with RO water at Ph 5.8 and add 2ml Cal Mag per Ltr, so 15ml and place your coco inside a old pillow case and leave to soak for 24hrs.
I do this twice, then i flush with pure RO water and make sure the run off is about 100 micro siemens,then your are ready to put plants into your medium.
Seedlings should be fed around 300-500 micro siemens, then crank up slowly.
Generally feed a day, nothing, water, nothing, feed etc, always leave a day in between for the coco to dry out a bit, before either feeding or watering.
Hope this helps.

Can someone also help me too. No one seems to answer my thread. 400w hps. Roughly 2 weeks and a bit into flower. Soil grow had nutrients in it. Transplanted once from solo cups haven't transplanted since. Cause I'm worried of stressing my girls since there flowering. Feed veg nutes once only to notice I over feed. So flushed them. Just seems since flowering I'm having issues. Unsure of my ph since I don't have a pH tester on me but will get one eventually. Run 3 fans.. but temp has dropped tonight I'm cold as so could imagine how they feel. So turned fans off lights out in 7 minutes please someone experience enough please help I don't want false information. Expert advice only thanks. Cheers. Pictures below. Someone said my girls need Cal mag an to use Epsom any ideas?

Whats the growing medium your using?, looks like bark chippings