Sick plants, need diagnosis!!

[BurnabyBud]

I have 3 plants growing right now, they all appear to be dieing. the bottom leaves on them have started to die, but the top ones seem un effected. they are under 4 cfl's 2600 lumins each, 2 x 6500k and 2 times 2300k. i am not sure on the ph, im gonna go out thise evening and im gonna buy a ph testing kit. Any idea's on what it could be?
here are some photo's, they are in schultz potting soil plus and are on a 24/7 lighting period.












and the saddest one of all

[BurnabyBud]

also, i use water filtered by britta, let it sit for a few days and water them once every 3 days.
it's a cush strain.

[trixman22]

First get ph under control or at least now what it is. Most potting soil has a ph of 7 so its a little high and prob has locked out some nutes. Is it a cush strain or a kush strain? Ive been told that Kush is very sensitive to nutes. Get a ph tester and then flush the soil with the ph'ed water. If your britta filter is newer then you shouldn't have to leave the water out for a few days. A good britta filter is almost as good as revrese osmosis(so I was told by someone who test water quality for a living).