Problems 5 weeks in flower

looking for some input on whats going on here. Its localized on newer higher leaves and is showing up on more leaves everyday. Other then that, and the heat stress the plants look great! I'm 5 weeks into flowering, growing in coco, 5.5pH and 1200ppm run off with daily waters. I'm thinking its Cal deff from the lowish pH? or maybe nute burn? what do you think?

ya def looks like calcium deficiency. Generally growing in coco you want to keep the PH a bit higher than true hydroponics but lower than soil. True hydro like DWC normally run ph at about 5.8 id recommend u aim for 6ish+. 5.5 is too low and it is likely hurting the plants calcium uptake.

nute burn will generally start at the tip and edge of leaves and yellow/burn, those mid leafe rust spots are classic calcium def. Those leaves look like they had very very slight nute burn (see yellowing tips) but the issue is PH.

purplehays1 said:

nute burn will generally start at the tip and edge of leaves and yellow/burn, those mid leafe rust spots are classic calcium def. Those leaves look like they had very very slight nute burn (see yellowing tips) but the issue is PH.

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Thanks for the response! I figured it was cal deff. Its nice to have the support from other growers.

Agree on calcium def and agree on higher ph as well I run 6.1 in coco

i agree, the conventional wisdom is 5.8 in coco but when i run under 6.1 i get what you got

Ya get that nice swing between 5.8 and 6.3 over the week and you can avoid them calcium issues I reckon.

Looks like either cal or mag deficiency. Both look similar.