Perfectly Healthy Plant Dies Randomly

I had 3 plants, now i have 2, the one, died randomly after 40 days into 12/12 and i vegged for at least 4 weeks.. it was perfectly healthy, it got fed and watered the same time the rest of them did everytime, i watered/fed them all about 2 days ago an they were all doing perfect.. i go an check on them and just the one plant has died, ALL the leaves are crunchy, and crumble, if there not crumbling, there hanging over... does anybody know what could possibly cause this? none of the 3 plants showed any signs of deficiency or bad health until now.. ALL the roots are still intact and strong, i can still pick up the pot by the stem, an mind you, it was a little moist from the watering.. .. soo sadd.. any input is appreciated..

Do you have any pics?

whats the temps and humidity?

its happened to the best of us, these are the precursers that cause this usually, soil was not mixxed well enough had a patch of basic or acidic soil shocked the sjit out off the plant killed it. or you didnt mix you water before feeding and nutes where concentrated at bottom and you feed that plant some powerfull stuff shocked the shit out of it killed it. or your pH was WAAAy off, or tap water was really bad(too much of something calcium iron chlorine) at the time you collected it for watering shocked the shit out of and killed. smell tap, taste tap, let it sit 12 hours, pH it and use it. different chemicals have different tastes you can tell.
another thing is genetics and or just a low tolerance to stress

All leaves shrivel and plant dies overnight can only be one thing , very bad nute burn, you sizzled it.