I have three white widow plants that are 4 weeks old and seem to be very healthy except some of the newer growth has yellow tips. PH is 6.8, room temp is around 78-82 degrees F, humidity 20%. Ive been changing nutes/water about every 10 days. I'm using Advanced Nutrients Grow @ 1TBSP per gallon/every water change, cal-mag @ 1 tsp per gallon/every water change and silica blast @ 1/2 tsp per gallon every other water change. I'm using the same mix to replenish water in buckets as needed until next water change. I'm using a 400 watt MH light on 24/7 hours for the Growth period. I use a small oscillating fan on low in the room to make thicker stems and diffuse hot spots. I also have a carbon scrubber hanging from ceiling and ducted into the a/c in-coming vent. What am I doing wrong? Please help before it gets worse.
Your pH is too high for hydro. You should aim for 5.5 - 5.8. Also, what's your nute concentration at? Do you have a TDS/EC meter? If not, you should really think about getting one. They're essential to hydro growing. Your leaves look like they're just starting to burn. That *may* be caused the the high pH, but it could be caused by too strong of a nute concentration. Get your pH corrected, and see if that solves the problem. If that doesn't help, then you need to back off your nute concentration by 100ppm per day until the burning stops. Once the burning stops, you'll know your optimal ppm for this strain. Make a note of it for future grows.
I have a Hanna pH/EC tester. I 've only used it for checking pH so far, because I really don't know much about the ppm end of growing. I lowered my pH to 5.6-5.7. PPM are 1040-1083, is this a good/normal reading?
Yes, 1050ppm is about right, depending on strain. Hopefully fixing your pH will solve your problem. Also, keep an eye on your reservoir temperatures. With your ambient temps as high as they are, the reservoir might get too warm. Ideal your res temps should be 65-70, although up to 75 is tolerable.
I'm always going to have temperature problem, I live in the desert. Lowering my ambient temp is probably going to be the easiest fix for me. With summer just around the corner, my a/c will be on 24/7 soon. I can probably tap into that somehow. I just had an idea; what if the aquarium pumps, that I'm using for my bubble buckets, were housed in a cooler location. Would that send cooler air through my water and have a cooling effect? Just a thought.
Yes, it can make a difference. I deliberately keep my air pump outside my hydrohut so that the air it's pumping into the res is cooler.