PLEASE help. READ and you will understand

OK please read... and please help . i know this is probably anoying and a nube thing to ask but i am not a nube .. im having a baby in about 5 months and this is my last chance to make some good money as i will not be able to do this sort of thing any more . basicly . my leaves are spotting brown and turning crunchy. heres a few pics and any help would be amazing . thank you so much

How is the new growth?

Old growth, the leaves you are noticing turning brown, are most likely being affected by lack of Mg.

the plants is about 4-5 weeks into flower . They are huge tho for indoors . about 5 and a half foot tall

Do you have a check of your humidity? In my area it is very cold and humidity is down to almost nothing at times. They need a certain amount of moisture in the air

Whats you ph light cycle grow medium etc. We need more info. It appears to be mg but usually mg is a ph problem. Not in all cases but usually