Problem wjth wilting 12 week old female (pics attached)

Ok so here's my problem

the attached images show a 12 week old female, she has been flowering for around 3 weeks now.

Everything has been going super good until this morning.

The top half of the plant is looking excellent and looks really healthy, but the lower leaves are wilting and not looking good.

She is on 12/12 lighting with a 600watt metal halide lamp. Ph is 6 with nutes now at 1800ppm.

Using Cannadian Express nutes.

I would point out that she has just been awoken from her sleep time when i photographed her (if that makes any difference?).

I have 3 other smaller fems that are not showing any signs of wilting.

All plants in same conditions in a grow tent, with fan on all the time, in a Wilma 4 pot drip system, with watering 4 times a day (for 15 mins).

Is the wilting normal at the lower part of the plant during flowering?

I have noticed that the leaves have thinned out alot since switching the lights as well?

how often do you water and how much when you do? that ppm sounds a little high man, i would try to not break 1500ppm, even during week 5-6 of flowering

they are being watered on a drip system. The system water the plant for 15mins, 4 times a day at the moment. The leaves dont seem to be showing any nute burn though.

One more thing i have just noticed. having placed her back in the grow tent, all four plants are very close together and im not sure if those lower branches are getting much light!! Would that make them droop. What's strange is that the top half of the plant is looking very healthy and strong, its just the lower parts that have drooped over

could be a number of things. droopy on bottom, to much water, droopy on top, not enough

you think maybe i should reduce the watering for a day or so to check if she recovers a little?

some plants "wilt" like that at night during flowering... theres been a lot of questions i've run into lately with the same sort of problem.. so it could be that..

BUT

your ppm is way high... 900-1400ish is plenty good... so your plant could be starting to show the early signs of nute burn...
it could be humidty build up since your light isnt running all the time and its cooler at night the humidty can build up and cause your plant not to "breath" as well and cause the wilting...

and the thinning of the leaves isnt much to worry about.. since its flowering it stops focusing on overall growth and just on producing buds.. all you'll see is a thinning of the leaves over the coming weeks.. until there are almost no leaves and just buds...

i think i will clean out my tank and lower the nutes and water 1 less a day to see how she goes

Ok I have lowered the nutes to 1100 (i know still a bit high but will perhaps reduce more tomorrow or day after). Also I noticed that my PH had gone mad!!! It had dropped from 6 (two days ago) to 4.8. So i have added PH up to get it back to 6, well actually its PH6.5.

When i added the Ph up the tank turned a milky white colour, i assume this is normal, having never had to use PH up yet.

Also i have reduced the watering down to 3 a day rather than 4. I felt the rockwool cube around the base of the main stem and it was really wet, so Im wondering if it has been slightly over-watered? I know that over-watering can cause drooping.

For the record i will update this post tommorrow with new pics so people can see if it had an effect.

I wonder why the Ph changed so much in just two days?

shit man i never realised it could move that much in just short period of time. I will check daily now. This is my fist grow and so far i think i have done ok, this appears to be my first problem and as she is sooooo gorgeous i dont want to f*ck it up.

Man i have been off the smoke for five weeks now and i can't wait to smoke her fat ass.