Plants leaves turning white from the lower leaves up

Hey guys ,
I have 3 8/9 week old pow 33's from ch9 , There growing in a polytunnel which has been quite hot for the past week and a half due to a heat wave . The leaves originally started going yellowish with brown dots but now they have nearly gone totally white .Im giving them hesi tnt complexe and there also in boi biz light mix .Has anyone else seen these kind of symptoms ? Kind of getting worried now !


http://imageshack.us/a/img6/4677/tzwt.th.jpg

http://imageshack.us/a/img20/5611/jvtz.th.jpg

http://imageshack.us/a/img42/1598/rxas.th.jpg

Leaves about a week ago .

http://imageshack.us/a/img818/5427/7e2h.th.jpg

Given your temps could be heat stress?

Peace

Dont think its heat stress since the temp's dropped last week and the problem still has not gone away , One of the plants has lost all its bottom big leaves and the other 2 plants leaves are starting to white also from the bottom up ... here are more photo's if it helps thanks

transplant into bigger containers and give some fertilizer.

Yes, I agree with polishpollack. Need some food and room to expand.

What is the new growth doing? The leaves you're looking at are old news the plants probably used the energy stored in those leaves when the plants got stressed because the stored energy is easier for the plant to get at fast when it needs it. Check the new growth and that will tell you what's up.