Hello. I have two plants (Afghan). Im growing in my basement so the conditions aren't the best. It's a little bit old and the humidity is pretty high so it grows slowly (they are one month old). But one of my plants ins kinda yellow. You can't see it well on that pic.
But in the comparison with the other plant it looks very bright and kinda yellowish.
DId I gave her to much water or did I vertilize to much? (I only did it twice) The other plant also got like this dry yellow edge on a lower leafe.
And can I water when its in the dark periode? I thought light for a few seconds doesn't hurt them.
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It's hard to tell in the pics but may have a pH problem with a little to much wind. Check for pests.
Please be careful with the inexpensive ph meters. After tons of problems and headaches it turns out my $20 deal of a ph meter was off by 1.5 points. You get what you pay for.
@Andrew: I agree pH is vital. …but at 20C and 90% humidity the plant can‘t transpirate. Temp, air flow, humidity, light all balance the three functions that are vital to plant growth: Photosynthesis, respiration and transpiration. Tilt any one out of balance of the other and trouble will come.
@OP: don’t water at lights out. Water at early lights on so the plant can begin to process the water. 90% of water is used thru transpiration. Plants don’t transpire at night. Also, lift the plant to see it it’s heavy for it’s size If so, don’t water. only water when the pot is lite.
water from the sink: ensure you dechlorinate your water by letting it set for ~48 hrs. Some municipalities use chloramine. If yours does use a granulated active carbon filter To remove it. pH your water to ~6.5 for soil. If your tap water is above 7 or below 6 pH some of the nutrients cannot be used. They each have an ideal pH and ~6.5 is the common pH.
I would suspect pH more than humidity issues. is getting a pH meter an option for you?
You should check out a vapor pressure differential chart. Basically, at 20C you should dehumidify to 50-65% RH in early veg. When you get the late veg/early flower lower humidity to 35-45% RH and in mid/late flower lower to 20-30%RH. Otherwise raise room temp or ideally a combination of both to get to 25-29C and appropriate RH for the new temp. high relative humidity can result in disease and mineral deficiencies Which could be the reason your plants are yellowing. If not the sole reason it most likely is a contributing factor.
It could be that there is not enough nitrogen based food for the plant in the soil or that the plant is struggling to uptake the food because of the soil conditions.
The solution to option 1 is simple: add more fertilizer
Option 2: if the pH in the soil is off the plant might struggle to uptake nutrients, measure the pH and adjust if necessary
Some more info about your grow will help.
What soil are you using?
What fertilizer are you using?
Are you controlling for pH?
What is the temperature/humidity ranges in the grow area?
What lights are you using and how far from the plant?
Finally, it is best not to disturb the plant during its dark cycle. You can get away with it here and there but I would not make a routine of feeding it in the middle of her dark period. Water/feed in the morning or right at the beginning of the night.