a sudden burst of rays "light can cause this maybe if it got to intense"as far as what they uptake i don't think so if it was chemtrails.."made up of alot of aluminum" that would make the ground to toxic.but u have to remember plants only uptake what they need.just like u or i..so all that would do is make it to where the plants could'nt eat.that could cause the plant to not be able to uptake certain nutes.but turning white does'nt go in line with that..if that was the case you would see the plant burn and or turn a bright pale lime green.where the burning would come in is if they were scorched or there ph was way off.."which can be caused by not having all nute as needed".what happens is the plant has say plenty of n and not enough k.this would cause ph to rise or lower.....