Yellowing/Necrotic Leaves Near the End of Flowering

[snowman4839]

Hey guys. Beginning of week 8 of flowering is tomorrow so I'm not TOO concerned about this since my buds are pretty much just finishing off right now but I'm just curious as to why it's doing this.
My Setup
12/12 light
400W HPS
fox farms nutes trio
pH'd every time from 6.5-6.8pH
Nirvana White Widow

The leaves are starting to yellow and die and I've heard that happens normally at the end of flowering but I'm just wondering if this is what is expected.

Fan Leaf 1

Fan Leaf 2

Also my other one's has it's leaves curling down. The tips have curled from excessive Nitrogen but they just new are curling down really badly like this

 

[Honkeycorn]

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[snowman4839]

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If I I got an answer from I chart like this, I wouldn't have asked. I know what N def looks like but it seems odd to be have it happen right now.

so the first one is Mn and N def.?
and the second is N def.?

and I still don't know what would cause the third pictures curling...

 

[snowman4839]

bump............. It just seem odd to have random defs. after they've been fine for so long after the same nute schedule