please help some shit is happening to my plants!!!!!!

ok the strain is white widow and i started feeding them house and garden nutrients a month ago and everything was fine but i noticed a small amount of the bottom fan leaves going purple brown towards the tip then spreads to the whole leaf eventualy making the leaf crispy brown and yellow and i don't think its nutrients because the ppm never went over 600 and i have the ph at 6.3 it has been getting worse and its climbing up the plant i did a grow last time with 3 white widow and 3 aroura the 3 white widow started the same and then pretty much were over taken by it and only gave me a lil bud and the aroura were fine i been looking online and the pictures dont seem to help me find out whats wrong i saw a pic of calcium deficency and it kinda looks like that but realy bad and i flushed the plants two days ago and watered it today with reverse osmosis phed water with a lil calcium and i dont know what to do if you can help me find out whats wrong please

add some magic green from h&g or some plain ole plant food with nitrogen, mag, cal, and all the other good stuff.

Pic would help? To better understand what you are seeing.

What is the NPK on the food?

i think its mag deficency i just read about it so i think i am going to water them with half strength nuts and two teaaspoons epsom salt per gallon and spray them with 2 percent epsom salt it said i should seem it get better in 4 to 6 days idk i will see and get back to you thank you guys

should i spray them at night? i have a 600w hps on in the day i dont want it to burn