Potassium def., or something else? [pics]

I'm still fairly new to growing and I wanted to find out what you guys thought might be the problem. If I'm completely wrong, please correct me.. like I said, novice here. ;)

This is my only female left in my cab, she's 16 days into flower (day 58 overall), LST'd. I haven't had a lot of problems with her, a couple def. early in her life, but those got resolved and she totally bounced back and was looking great. However, I got a couple other problems arising now that I think might be a K deficiency. Or maybe a low soil ph? I know it's optimal at 6.8, and mine is kind of low.

The reason I think it's a K def. is because on the older leaves, the margins are yellowing, burning, then dying. The leaves are turning a kind of dark yellow, with some green left in the veins. I checked out Ganja Guerrilla's site, and a couple pics under the K section really show what my plant is doing. And I don't think it's a nute burn of any kind? Also, the newer growth tips are a little curled; the margins are slightly curled under. I wasn't sure if this was normal or not.

Or I think it might be a pH issue.. but I haven't changed anything with the water since she was a seedling, always tested pH, and everything has been fine up until 4-5 days ago. Is my soil pH really too low? And how would I correct it?

She hasn't been fed nutes since I flipped to 12/12; I only gave Epsom salts once since the 12/12 flip, and tonight I fed her some molasses (1 tbsp/gal).

Soil: Been in the same soil since 3 weeks old, had no problems with it. Scott's Premium (7-4-3 or something like that), 1/8 cup each of bone/blood meal, perlite. 10" pot
Soil pH around 6.2, but might be inaccurate
Tap water pH at 6.8-7
Temps: 83 day/74 night
Humidity: 35 day/50 night
She's under 6 - 42 watt of 2700K CFLs (250 watts total)
Good ventilation and air circulation

Any help is appreciated!! :)

Hydro and Soil less Mediums

Potassium gets locked out of Hydro and Soil less Mediums at ph levels of 4.0-4.5, 6.0-6.5.
Potassium is absorbed best in Hydro and Soil less Mediums at ph levels of 4.7-5.3, 6.7-8.5. (Wouldnâ??t recommend having a ph over 6.5 in hydro and soil less mediums.) Best range for hydro and soil less mediums is 5.0 to 6.0. Anything out of the ranges listed will contribute to a potassium deficiency.



Solution to fixing a Potassium deficiency
Any Chemical/Organic nutrients that have potassium in them will fix a potassium deficiency. Again Peters All Purpose plant food 20-20-20, will cure the potassium deficiency , Miracle grow Tomato plant food, Miracle grow All purpose plant food.( Only mixing at ½ strength when using chemical nutrients, or it will cause nutrient burn!) Some other supplements of potassium are: Wood ashes, which are fast absorption, Kelp Meal, which is medium absorption, Greensand, which is slow absorption, granite dust, which is slow absorption. Sulfate of Potash, Sulfate of Potash Magnesia, Muriate of Potash, which are medium absorption. FOXFARM GROW BIG HYDROPONIC CONCENTRATE, which is fast absorption. (FFGB can bring your ph down as well) Earth Juice Meta-K, which is fast acting. (Can bring down your ph as well) Leaves will never recover, but the plant will show recovery after about 4 to 5 days when using a fast acting nutrient.:thumbsup::thumbsup::thumbsup:

Thanks for the reply, Haze!! So you def. think it's a K def?

Is it just because she's hungry, or could the K be locked out due to my possibly low soil pH? I need an accurate way to test soil pH... any suggestions on doing this without the help of a pH pen or something? I've done the waiting 30 min. after watering, and ran a little distilled water over the top and tested that runoff.. but it seems I'm just getting the pH of the water I ran thru (6.0), and i'm sure that's not totally correct.

Will watering with molasses help the def., or do I need to use something more/stronger?

Soil

Potassium gets locked out of soil growing at ph levels of 4.0-5.5
Potassium is absorbed best in soil at a ph level of 6.0-9.5. (Wouldnâ??t recommend having a ph of over 7.0 in soil) anything out of the ranges listed will contribute to a Potassium deficiency.

you must get a p.h testing kit ,the p.h. is the key.
goodluck:thumbsup::thumbsup::thumbsup:

Overwatered
Soil pH too low
Toxic salt buildup from being in that pot too long without a flush.

Flush at water pH=6.9 (high end of the acceptable range, to raise the soil pH). You need to get those salts out of there or the stunting and burn is going to get worse FAST. Use 3x the volume of the pot and then feed with a COMPLETE fert with micros at ~1/3 the recommended dosage.

Potassium def presents as reddish speckling of the lowest leaves. Simply looking at the pH range lockout chart doesn't help until you already know what the physical symptoms presented are.