Help me diagnose this problem?

[basement grow]

Three leaves on one stem of one plant exhibiting a new spotting of copper colored necrosis. I am guessing it is the new hotter mix of nutes, however, it is only showing on one branch of the plant like this. My other thought was Mn deficiency, but no other plant is showing it, and my pH is under 6.2 which should keep it from locking out.

Plants are in hydro/dwc under a 400w HPS using GH flora series at 70% with 35ml of floranectar per 5 gallons of water. pH is 5.6 - 6.2. Day 48 from seed (autos) 2-3 weeks til harvest. Affected leaves are not in range for heat stress, and have not been misted while under lights. No pests. Air temp around 80F. Res temp 69F. RH 55%.

 

[PitViper]

do a good flush and run water from the top down...on all of them. check the PPM of the run off. start with fresh water and set it to 5.8, I think you have some salt buildup on the one. after the flush wack it to 100% and you will see fresh growth almost overnight. the damaged leaves are trashed but leave them on unless they are 50% damaged

 

[basement grow]

do a good flush and run water from the top down...on all of them. check the PPM of the run off. start with fresh water and set it to 5.8, I think you have some salt buildup on the one. after the flush wack it to 100% and you will see fresh growth almost overnight. the damaged leaves are trashed but leave them on unless they are 50% damaged

Thanks, man! It has been 2 weeks since I flushed the netpots with straight water, good call! +rep!