Possible P deficiency? please help

Ok i made a list of possible problems in order from most likely to least likely please let me know if you think im right or way off track

1. Nutrient Deficiancy-

Possible because-
The most I have fed is half strength and i only feed every second watering
My BC could be a heavy eater and that would explain why it is only effecting this plant
It looks like it matches up with the issue on the chart

Lockout caused by crazy PH-

Possible because-
I dont have a PH meter just using tap water
Could be a sensitive plant which would explain why its only effecting this plant

Inprobable because-
I have only fed a max of 1/2 str nutes and feed every second watering
Tap water is usually good and if the PH was this out it would probably effect the other plants at least a bit

Heat stress-

Possible because-
The temps have been fairly high at one point close to 90°

Inprobable because-
It is only effecting the bottom leaves
None of the other plants are effected

Bugs-

Possible because
I leave the door open occasionally to let the room cool off

Inprobable because-
The intake and discharge are both filtered
only one plant is effected
doesnt look like bug issues

Also today is feeding day so i would really like an answer from someone who has experience this, if i dont get any then i guess i will go with my previous diagnostic

your stems would be screamin' red/purple, if you had bronzing/necrosis from P lock-out/def. imo

don't feed. less is more. water if due. imo

Ok thanks for the advice, But i havent been feeding much at all... im using a soil-less mix so it has no nutrients in it and since its popped ive fed once with 1/8 str nutes twice with 1/4 str and once with 1/2 str

they are ugly spots fer sure. idk............and i'm totally blazed

Phosphorous deficiency is rare especially in a plant that young. Try a couple teaspoons epsom salts in a gallon of water for your feed and nothing else. Then just water for young plants for a couple weeks. Yes I know people feed and they survive or even thrive but KISS.

Originally Posted by B.B.V.C.

Ok thanks for the advice, But i havent been feeding much at all... im using a soil-less mix so it has no nutrients in it and since its popped ive fed once with 1/8 str nutes twice with 1/4 str and once with 1/2 str

it could have gone without any nutes at all, from the size of it

IMO the nutes are the problem