3ft plant 3wks into flowering, immediate care needed!

right now i have 6 different strain plants flowering under a 600w hps in a 3x3 tent, temps range from 79-85 when lights on, 5 of them look amazing, however i have one that recently took a bad turn.

its got these spots where the leaves start to turn grayish brown, starting ether on the tips or just in random spots on the leaf. then the rest of the leaf pales out to a yellowish color and dies. started lower on the plant, slowing working its way up. other than this problem the plant seems okay, its 3wks into flowering and has started to pop up some nice buds.

pics


its approx. 36in tall, 3gallon pot with a mix of MG potting mix and FF ocean forest, been feeding FF nutes every other watering (worked up from 25% to 75% rec. dosage) this strain i belive to be sour cream.

my next move was going to be stick in the bathtub and flush it with a few gallons of water.

any advice is MUCH appreciated.

i would flush and feed half strength nutes & see what happens.looks like too much nutes to me.

that looks like a bit of P burn, did your MG soil have the little nute balls in it? what is the ph of your runoff? if the MG had nutes in it and its been less than 8 weeks since you transplanted then flushing could make the problem worse.

no nute balls in the mg soil i believe, it was mixed 50/50 with FF soil and i never transplanted them, seeds started ~9wks ago directly in 3 gal pots.

my ph meter is cheap, and also uncalibrated at the moment as it needs re-tweaking every other week with special soluition. it says my tap water is 7.9 and my run off is 7.2, although typically in the past when i have calibrated my meter, the tap has been between 6.9-7.3 so realistically my run off is probably around 6.3-6.5

get that meter calibrated!! its best to keep those cheap meters stored in calibration solution the bulb dries out and clogs up easier than the pricey ones. if the MG didnt have nute balls then i highly recommend flushing. also trim off any severely damaged leaves, more than 40% dead it should come off. trim any brown crumbly parts off the leaves too, any dead or damaged tissue is an invitation for disease.

what nutes are you using? if its the FF trio (Open sesame, beastie bloomz and cha ching) then 75% of full dose is too strong. plants dont actually need that high a ratio of phosphorous. if its their standard nutes then flushing should fix your problem. be sure to water with 1/4 strength nutes after flushing to prevent any deficiencies.

i just flushed it out pretty nicely and got rid of the death... ive been using combinations of FF grow big, Tiger bloom and big bloom.. only tiger bloom and big bloom for the last 2 weeks though.. tigerbloom says 2 tsp per gallon on the bottle and on my last feed i think i did 1.5 tsp. after it comes back from this flush ill start off at just 1/2tsp again, and 1 tbsp of the big bloom (says 4 tbsp on bottle)\

thanks for the responses! ill update this thread in a few days with results