Need Help Identifying Problem

[Botani]

Hello everyone! Im growing a dank granddaddy purple crossbreed that i created a while back and i just cannot seem to shake this discoloring of the leaves it gets every grow that comes on the leaves around day 40-50 of flowering. i have a ton of other strains in the same system and they are all doing great. hell this plant is doing great as well there is not a blemish on it anywhere except the biggest fan leaves here. i cannot figure out what is causing in this. my grow is immaculate even better than probably every single profession commercial building out there. i have all state of the art expensive monitors and equipment and i only get this problem with this plant and only on its biggest fan leaves. every other leaf and bud is perfect. my temp is perfect. my humidity is perfect. my ppms are dead on perfect. my ph is dead on perfect. my light distance is perfect. i have a $20000 air exchange unit and heating and a/c and humidity control. perfect co2 perfect oxygen in rdwc tanks. perfect water temps with $10000 chiller. and this is happening. i at first thought it was calcium issue but now for 3 grows of it i been playing with the calcium and still no change. maybe its just the strain?

 

[013]

Hey Botani,

RDWC huh? It would help to have more info, what nutes, any amendments, how often do you feed etc plus a few pics. Sounds like you’ve got it going on over there with a high tech setup but maybe something will jump out? But yes absolutely it could be a funky strain.

 

[Botani]

the nutes we use are trz nutrients from therootzone they are a private company and have been for many years i just get lucky enough to use them because of relations however i have used everything in the past gh, an, h&g and dutch etc.. and nothing gives the results like trz but anyway they are great and it is only this plant.
each system is 125 gallons with 48 plants per system so the ppms are at a constant 900-1200 strain depending and if it needs more or less. i use hydrodefender which is trz's version of something you might know as taratuntla or great white or hydroguard.

but yea i dunno im pretty good with this stuff and i mean the plant is amazing i will get some pics of the plants that i took those fan leaves off of. they are utterly immaculate its just weird because like i say every single grow at around day 45 or so only the odd biggest fan leave goes that way and everything else remains perfect.

 

[013]

Was thinking of rust or leaf septoria but I’m a soil guy and it sounds like you need a heavyweight like @bluter

 

[bluter]

would have to see the whole plant but looks like it needs phosphorous.