Yellow Leaves and oh so many possible problems

So this is my first grow. I started out with the intent to just let it grow in the sun in my window, but now have it flowering in my panda film lined closet under a 250w HPS. I found I got really enthusiastic about growing (surprising, I know).

Now, my plant has always had shriveled and brown leaves at the very bottom of the plant, which I think might have been a magnesium deficiency, but I didn't worry too much, since the rest of the plant was green and relatively healthy looking.

When I moved it under the 250w, I noticed some yellowing and a little browning on the top leaves, which got worse after another day. I assumed it was heat stress so I moved the fan to blow at the top of the plant which stopped any further browning. But the yellowing has gotten worse and now affects more leaves towards the middle of the plant.

I could easily have overfed it, on my last feeding I gave it Botanicare Bloom, FoxFarm Grow Big, and some CalMag. Small amounts of each, but it still could have been too much.
I also finally checked the pH for the first time on sunday. I got a water test kit with up and down. I discovered my tap water was very basic. So I then ran some ph'ed water through my soil, and it came out basic. I flushed with a few gallons of acidic water, and by the end the soil pH was lower, but still a tad basic. I was afraid to do any more, as all the water was already compacting my soil. The water had come out a bit green through all the flushings, pretty clear by the end but not totally.

I put some sand on the top of the soil after I flushed it, in an attempt to thwart the gnat problem that I noticed was beginning. I realized afterwards that this might not be a good idea, as it might make the soil take longer to dry, and it's pretty saturated at the moment. It had been a couple days since I had last watered the plant, but with the flushing I could be over-watering the plant.

The other potential issue is ventilation. It's in my closet, which I leave slightly open with a sheet of panda film over the opening. I have a fan blowing while the light is on, and so it doesn't seem to get too hot, but I am worried there might not be enough air exchange. There's a hole at the top where air can vent out of the grow area into the top of my closet, and air comes in along the side of the panda film covering the door. But this might not be enough, especially at night when the fan isn't on, which I think is positioned to pull air in.

So, what do you think is my biggest problem at the moment? Heat, too much nutes, over-watering, poor ventilation, too high pH, gnats (unlikely, there were only a couple) or something else entirely?

im no expert, im on my first grow and having similar issues. the browing at the top could be from your light but the browning in the middle is very unlikely to have been caused by the light. the browning on the tips of the leaves usually indicates nute burn or a ph problem. Knowing your exact ph would be a little more helpful. If your ph is between 6.5-7 you should be ok there but 6.8 is usually prefered. I would let the soil dry out and then flush it really well. use 3 times more water than the size of the pot so you would flush a 1 gallon pot with 3 gallons. if you read book and look at forums alot of people get complex with their nutes and atleast to me they make it seem like these plants are nutrient hungry beasts but in reality they dont need all that much fertilizer.

10 - 4 , that's a definite over fert.

FLUSH IMMEDIATLY

Besides the brown spots, the yellowing of the leaves is normal during flowering.

Raise the lamp a bit too - I had the same prob.

Good luck!

-Rich

Your plants look very hungry and deficient of nutes. You should have corrected the problem with the ph'ed flush, as I believe the nutes were Locked out from the ph being so high as you described. I would introduce 1/4 strength PH'ed Nutes until you see a responce, then increase. I DON'T believe heat or ventilation has anything to do with the problem as I dont see any heat stress, and I dont see Over fert either.

I have found the Hot Shot to be the ABSOLUTE best pesticide out there for things like mites and fungus gnats. Be sure to get one and follow the directions. They are not intended for areas that will be occupied for more than 4 hours per day. But it works very quickly. I use it for 2-3 days at a time, then put it away in a ziplock bag. It killed every mite in the room in 1-2 days. Hehehe Never spray your plants again for mites and/or gnats and many other garden pests. Its not the flying adult Fungus Gnat that is hurting anything, it is the tiny larvae in the soil eating your roots and opening them up for more disease and rot. Take care of these ASAP!

http://www.lowes.com/pd_69690-316-1...ctId=3067945&Ns=p_product_quantity_sold|0

Good Luck!

Based on what you've said and from your pictures, I'd suggest this is a fungus and not a overfert, underfert or flushing issue. You need air movement and ventilation in that closet. You don't mention your RH but I'd guess over 70%, which will cause fungal growth...spreads fast, leaves will almost appear to be decomposing. Remove the worst parts of the leaves and spray with a fungicide, miticide safe for garden plants.

Thanks for all the responses.

I doubt it's a fungus problem, since I'm pretty sure the browning was caused by the lights, and I'm guessing is a separate issue from the yellow. I haven't noticed much improvement since I flushed on sunday, but I haven't been able to check since tuesday morning, so I'll see tomorrow if it helped.

If I wanted to check the pH again and possibly flush it should I wait until the soils dried out so as not to risk over-watering? Also, how long after flushing should I wait to add more nutes, is the next watering fine? I would probably add a very low dosage of bloom, grow and calmag.