Arobskittle
Bluelighter
where the hell is prelude? how them yellow bitches doing?
So here’s what you’ll need to perform this simple experiment:
(1) Distilled water (purchased from any grocery store)
(2) Coffee stirrer (or other thin, clean object with which to stir)
(3) Bottle cap (Snapple bottle caps work perfectly)
(4) Empty wide-mouth jar with lid (like an old mayonnaise jar)
(5) Tablespoon of plain table salt (I suggest Mortons – it’s made in Chicago)
(6) Your hygrometer (duh)
Place the tablespoon of salt within the bottle cap and slowly add distilled water to the salt while stirring with the coffee stirrer. Only add just enough water to moisten the salt so that it becomes a thick paste. Do not add enough water to dissolve the salt!
Place the bottle cap with salt gently into your wide-mouth jar and add your hygrometer. Make certain the sensor is exposed and is not blocked by the sides of the jar. Seal the jar so there are no leaks and put it in a place out of direct sunlight and with a stable, cool temperature (like your closet).
Leave the setup undisturbed for a minimum of eight hours. After that, check the reading on the hygrometer through the glass jar – it should read on or near 75 percent relative humidity.
Due to the salt paste reacting with the confined air, the ambient relative humidity within the jar will be exactly 75 percent. Most inexpensive hygrometers are only accurate to within 3 percent, so do not be surprised if yours reads 72 or 78 percent. Whatever it reads plus or minus our 75 percent benchmark is the amount of error of your hygrometer.
If your hygrometer has an adjustment potentiometer then, by all means, try to tweak it to exactly 75 percent relative humidity. You should repeat the salt calibration test after making any adjustments. If your hygrometer can’t be adjusted but the reading is close, then my advice is to not worry about it; just remember that your hygrometer is X percent off – either high or low. If the reading is grossly in error and you are unable to adjust it, you need to replace it.
I don't think it's light bleaching that's causing the severe chlorosis (aka yellowing in plain English). The tops look like they could possibly be a bit scorched, but it's hard to tell whether that's from the lights being too close. I doubt it if I'm truly honest though. But hey, you never know what the issue could be at the end of the day.
Edit:if some plants are only 8" then that's too close mate.
Prelude, are you able to give EC readings as opposed to ppm? Or does your meter only read in ppm units? There's no 'set' ppm you should be giving your plants.
Prelude, feed your plants at 50% the "regular" dose now at every feeding. Otherwise you might end up at square one again.