Flowering Plants leaves turning yellow

I am about 32 days into flower and there are alot of leaves turning yellow and withering up. The flowers look fine, it's just the leaves. Anyone know whats up?

Ph 5.2
PPM 1150
temp 77.7
humidity 47%

other 5 plants seem to be doing fine and are nice and green. Some smell danky, some smell like hay...I don't understand. help?

400 watt hps light is 4-5 inches from tops of tallest plant and about 12 inches from the other plants.

they should be done in another 2-4 weeks and it could be the buds are sucking all the nutes from the leaves,Ima new at this as well but I am told yellowing leaves are normal for some towards the end of the plants life.As I said I ma new here as well but you should wait for somebody else to answer as well but I think I am right and also if it not that they could be hungry for more nutes,good luck friend........

The soil may be too acidic, and it seems like this is about the time where you can have this problem...the way I avoid it (and believe me, it's happened a lot to me in the begining) is by proactively giving it one or two mini flushes late in veg and as you settle into flowering. Not sure what biologically causes the ph swings, probably a build up of salts from your water and nutes...btw, make sure you use warm water when you flush and let the plant sit for about half hour between flushings.

The inconsistancy in smell is not a good sign..those hay smelling areas are losing potency because the ph lockout is severe, especially if they're on branches that have lost fan leaves.

Final thought, make sure you're having good run off when you water, use perlite to reduce moisture retention. (next time)