Please Help Plants Leaves From Bottom Up Falling Off!

Ive been growing for a few years and ive never had this problem before. At first I thought it was spider mites because I had a slight issue with them around week 1 but ive sprayed them down and few times and now i havnt seen any. It started with the leaves falling off at the very bottom but now its working its way up the plant and I know this isnt the normal yellowing and falling off that this plant does in flowering. If anybody could give me an idea of whats going on that would be great. I dont know if its a defienceny, ph problem, over watering, over fertilization or what. Please help I need it before I loose my whole plants.

The plant was started from clone and planted in that pot around the begining of August.
The PH of the water after its adjusted is 6.5, I never have checked the run off. Soil test said it was around 7.0
Yes the stems are soft leaves towards the bottom snap off very easy.
I feed them nutes every other watering which is usually every 4 days or when the pots are light.
Im feeding them fox farm nutes: Right now its Tiger Bloom, Big Bloom, Beastie Bloomz(Soluble) & AN Bud Candy (I follow there feeding schd.)
Soil is a little compacted but not to bad
Soil does have perlite about 3 parts soil 1 perlite 1 vermiculite
Pots are 3.5 Gal
Plants are on Day 23 of 12/12 light cycle under a 600w hps
Rel Temp is usually 80 with humidity of 65% I do have a fan blowing and an exhaust system to reciculate the air. I dont foliar feed them but i did have to wash them off a few times for mite problem.

I hope this is some of the information you are looking for and attached are the extra photos you asked for.
Thanks again

an you also take some pictures of the full plants? It helps if it can be put into perspective. Leaves do die and fall off, it's natural. I'd rather see the plants than just the leaves.

Looking at the leaves alone, N defficiency is probably ruled out because of lack of yellowing. A K deficiency is more likely, going on the leaves, however NP or K could be the cause going by the abuse chart. I'm curious what your PH is and how long ago this plant was started. Are the stems soft? How often are you feeding it and with what? Is your soil compacted? How long has it been in 12/12? There is a lot of info that is needed beside a few pics of leaves. How often are you watering? Does the soil have perlite? How big is the pot?

Serpis I updated the information and pictures you needed above

Does anyone know if maybe this is a (P) phosphorus deficiency. Some of the plants are showing some purple on the buds & stems. Also the stems are very soft and the leaves break off easy. From the bottom up the leaves have been getting a brown at the tips & edges then it works its way into the leaves until the leaf dies and falls off.

NateDizity1420 said:

Does anyone know if maybe this is a (P) phosphorus deficiency. Some of the plants are showing some purple on the buds & stems. Also the stems are very soft and the leaves break off easy. From the bottom up the leaves have been getting a brown at the tips & edges then it works its way into the leaves until the leaf dies and falls off.

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if i were you i would really check the runoff. it looks to be a couple of things which usually means ph in my experience, but yes that absolutely looks like a lack of phosphorous. depending on your water supply your soil could trend toward acid or base. mine always tends toward acid no matter what the ph of my watering, but plenty of people using almost identical gear to mine have soil that trends alkaline even if they use the same brand soil and nutes. phosphorous gets locked out when the ph is below 5, and with the nutes you're using there should be no deficiency in that at all. i vote ph.

Thanks totalhead im writing down any information I can get, Im going to check the run off next watering which Im planning on giving them just straight ph'd water to flush my pots out. Thanks for your input

Try some calmag+half strength veg nutes.

should slow down the yellowing/ off

so what did we decided? I am 2 weeks into flowering & she is dropping her leaves like crazy! I am baffled, the leaves/stem that falls off looks perfectly healthy, just snaps right off at the stem. why?!?