Jimi's Tips,
Learn To Read Your Plants.
When I first started growin indoors years back I started out buying every meter, test equipment, even run off test for fertiliser, and anything like that, then an oldtimer told me "Learn to read your plants" , I really respected his wisdom so I took it to heart and have forever been thankful that I did listen to him. He said "if you are ever going to be a succesful grower, you will use that advice". It was the absolute best advice I could of got.
So when I did start I would look every plant over and try to diagnose any problems whether it was nutrient defciencies, ph problem, a disease or infestation, and then I would check with my equipment to see if I was right. Disease and infestations, please use the plant doctor that I posted earlier in this thread, wait here's the link.
https://www.growweedeasy.com/cannabis-symptoms-pictures
That went on for about the first crop or two, I don't even know where any of that stuff went but around here somewhere. Now, and for the longest time, I do everything by eye.
I can't stress enough how you should look every plant over thoroughly. Check leaves top and underneath. Just by spending some extra time with your plants you can learn so much more about how they grow.
All plants will
TELL YOU just what they need, so pay attention and your crop will thrive.I use
NO feefing schedules as I visit all of my plants every day, if they need something I will see it before the meters will.
So to test your skills diagnose this
This is good practice

. Post any answer you have and by all means use the plant doctor. I'll post the answer in a week or so.