Marijuana plant distress

A question from a fellow grower:

This is my first grow attempt and things seemed to be going great until several weeks ago. My plants are in great distress, with leaves yellowing and then turning brown and the stems are turning red. I’ll give as much info as possible
…I am growing gold leaf, 10 plants in 3 gal containers. there are 5 plants each sitting on two large trays on the floor. I am using a 600 watt HPS bulb at 12 hours on. The room is at 78 with the light on and about 65 to 70 when off. The humidity is at 41. I am using one gallon bottles of tap water with the PH lowered to 6.5 and 4ml of the THC booster. I pour two gallons into each tray (5 plants) initially every third day. At week 5 in the flowering schedule, it indicated to NEVER let the plats be without water so I went to every other day. Someone on the site communicated that I might be over watering so I went back to every third day, but the plants seem to be getting worse…IS THERE ANYTHING I CAN DO TO SAVE THEM???

Just because you are sure of the pH of the water, or the nutrient concentration, EC/PPM, being given to the plants doesn’t mean that is what has accumulated at the root zone. It is highly likely you are suffering from pH imbalance at the roots, especially as you say you are seeing red stems, red stems is most often a sign of a nutrient lockout due to pH or overwatering. With plants as big as these and the look to their leaves I’m much more prone to think nute burn and pH imbalance than over or under watering.

Quick fix dude is to just get a good plant mix for vegetables and just re pot them. Trouble is with people they see change and panic, then they add nutrient, which can be to much. They panic again and add more or attempt a flush and all this shocks your beautiful plant. Shade leafs will go yellow and die when budding as that is where the plant stores its nutrient, this is where most 1st time growers panic and kill there crop.

I think the plants are too big to risk repotting. Will a good flush stop the nutrient lookout? And seeing how this is my first time, how much water do you use to properly flush plants in 3 gal containers? Thanks for your help!

Another question, buds are already starting to turn orange…should I be concerned at all about the leaves? Today is the next scheduled water day, should I give them a really good flush?

Yes. 3 gal containers are the absolute smallest container ive managed to grow successfully in, however, its tougher than larger containers like a 5gal bucket. I had to flush my 3 gal pots with 9 gals of pH’d water before the runoff would be the same ph and ppm as the water pooring in the first time i ran into your issue. Ended up flushing my pots with just water once a week at least, in 5 gal buckets i only need it every two or three. I feed alot though, every day, but i use H2O2 in my nutrient so i CAN feed it everyday without drowning the plant.
Make sure you flush with pH’d water, thats the only way to mess that up. And then feed after and let he soil completely dry out before nexf feeding. I flushed more during flowering than, veg, had more pH issues during floweri g too. Good luck

Thank you for your feedback, very much appreciated.