Help!!! Tops of plants yellowing nutrient def. or pests?

Hello everyone. I have a couple ladies growing outdoors outdoors in full sun and smart pots. About a week ago I noticed that the The fan leaves toward the top of the some of the plants started to turn yellow and droop. Growth in that general area (top 2 feet) seems to be retarded. There is also some yellowing of the leaf edges and tips as well as twisted bud leaves that seem a little slender. Not sure if this is related. I have been asking around and have been getting mixed advice. Some think its a sulfur or zinc def. While others have said it could be a pest infecting the top of plant. The water I use is in the high at about 7.8 is that too high? Could that be locking up my micro nutes? Any input welcome thanks a bunch guys.

hi @Tawn and welcome to RIU. you have a really nice outdoor grow going on-great area.

here's a bump for your thread - there are some really great outdoor growers here and i'm sure they'll get you squared away soon.

Yea 7.8 is too high. U wanna be as close to 6.5 for soil grows. U start to lock out some micros. I lost a giant diesel to this...at least a pound plant. If u are flowering time to get a hold before it gets to far behind. Once u start flowering the plants biological clock starts ticking so to speak. Depending on what deficiencies the plant has, flowering will slow to a snails pace until u correct it, and depending on how long it takes for the plant to recover, it might not even be able to finish flowering before it dies. But that usually affects the entire plant, not just the top two ft. Pests are another possibility if only affecting a section of the plant. I've seen small boring insects only affect entire branches while the rest of the plant remained vigorous looking. So look over the plant in its entirety for signs of pests. Little holes in the stalk right below where the plant is affected. Good luck!

Ph is the issue, it is causing potassium absorption issues. You need to first correct the PH then focus on a 5% - 10% higher potassium increase on them.

Okay cool. Thanks 808, my fist outdoor grow this scale also thanks for that graphic. That is really helpful. So I have been watering with 6.5 for about a week and the growth seems to have resumed, although the tops of the plants still are yellow and it is spreading really slowly. Do yall think I should hit it them with micronutrients or should there be enough in the soil since it is no longer "locked"?

i'm not an outdoor grower, but your new growth is yellowing and the bottom of the plant looks fine; symptoms appear on new leaves-the problems could be related to iron, zinc, manganese, copper, boron, chlorine, calcium, or sulfur. also, are you sure there aren't bugs? no offense to other posters, but there's something else going on besides just the pH being a possible issue.

Okay that's what someone at the grow store said. I have inspected them and I don't see any bore holes or fungus growing on the surface of the leaves. Is there some sort of fungus that could be in the main stem? If so what products could I use to treat a systemic fungus?

i wouldn't start thinking of products to treat them with until you know the problem. i've recently learned there are bugs that you need a microscope to see (the same thing used to check your trichomes), so until you know the problem, proceed cautiously and with patience. what's been the regime with them so far?

once again potassium is the issue from the pics, it looks to be pretty moderate. Those leaves may recover but the major yellowing may cause slow growth