Should i harvest??? Please Help

i have 8 large Purple haze and 28 purple kush going into 30 days of flowering now and the buds are still really small especially at the bottom, the tops on most look really resiny and small buds which i assume will still grow bigger, i'm using 2 1000 watt bulbs also im feeding them with big bud and a host of other nutrients my local hydro store recommended but the real problem is that today i noticed that one plant in particular was looking really old and the leaves from top to bottom are really dry and are about to all fall off, this is the only one like that so i was wondering what the causes may be and what i could do to save the plant?

i'm really resisting the urge to harvest them now but i know it's been a while in the flowering stage more than 4 weeks and i've been looking at some other photos on the site and now mine dont really look so ready or large to me anymore as is so any help would be greatly appreciated.

playboypaul
thank you

the bad one:




the good:



the rest:



the early stage (1 month ago)


P.S. i have 8 purple haze on the outer corners since they are so large. and there's kush in there for the rest of them and they are considerably smaller but budding nice but really slow i think, i need help to know when to harvest, the thc is really plentiful all over the plants so im not sure when to cut them and i dont want to do it to early

help please.

 

http://icmag.com/ic/index.php? Search for the complete guide to sick plants, ph etc. This site has some great diagnostic pictures, by scrolling around you should find your specific problem as well as the solution to the problem. 30 days into flowering seems early to be winding up altho I'm not familiar with those 2 strains. They don't look ready yet. There is a sticky someplace on this forum - I think it's on this forum, maybe in my grow book, but it gives a good look at ready to go buds, course every strain is a bit different

 

Here's my suggestions:

First, examine the leaves of the affected plant(s) carefully, both top and bottom, looking for mites. Spider mites are about this big >.<
If no mites are presnt then my guess is a nutrient imbalance.
This is gonna be a lot of work, but start by flushing all the planters. I couldn't tell what size your are from the pics, but you need to use 3 times the amount of the capacity of the planters of pH-correct plain water. So if your plants are 1 gal size, use 3 gallons of water. Elevate the plants on bricks or something so the run off doesn't get into the other plants.
Then next time they need watering us a high-quality flowering nutrient, 3/4 strength at first.
Your plants should perk right back up.