To me it doesn’t look like a magnesium deficiency so I don’t think epsom salt would do the trick.
Just so you know if later you do need to treat a magnesium deficiency with epsom salt you can top dress and water in or add to water at about 15ml per gallon or about 3 ml per quart foliar which will get it to them quickest.
This is how the leaves look with magnesium deficiency
Tough to diagnose without knowing more about your set up and picture of entire plant etc.
is it only that leaf? Could have spilled nutrient feed on it etc
No it’s on other leaves. I don’t use any nutrients. I’m real careful not to water or touch the leaves
Can fill this out so we can continue to help you in the best way possible? Necessary to know information.
COPY/PASTE: This “Support Ticket” into your forum post.
Answer these simple questions the best you can.
If you do not know, or do not use something; Just say so = NA
Strain; Type, Bag seed, or NA
Soil in pots, Hydroponic, or Coco?
System type?
PH of runoff or solution in reservoir?
What is strength of nutrient mix? EC, or TDS
Indoor or Outdoor
Light system, size?
Temps; Day, Night
Humidity; Day, Night
Ventilation system; Yes, No, Size
AC, Humidifier, De-humidifier,
Co2; Yes, No
Add anything else you feel would help us give you a most informed answer. Feel free to elaborate, but short, to the point questions and facts will help us help you 
Looks like you are going to need to invest in better lights here very soon
Honestly that looks more like variegation than it does a deficiency. Odd it’s on two plants. Are these from seed or clone?
I agree 100%. Surprised it’s not symmetrical n the other side. This is just genetics, and nothing you can do.
I had a Super Lemon Haze that had a variegated leaf, just on half of the fan leaves.
When I cloned it, I forgot to label one, figured out which one that one was real quick.
Realistically the rest of your plant looks great, well fed. Generally deficiencies show symmetrically and uniformly across the plant. This is why I agree with the variegation.
They are not clones. I germinated them from random seeds I got out of a bag
First time growing. Not sure what it is. I thought it was magnesium def. No way it’s water damage. I am really careful watering. I don’t have a ph tester so I boil the water. Temps stay at 75 and the humidity is always at 60.
That’s weird. Doesnt look like water damage. You should really get a PH meter. Even the cheap 15 dollar ones are pretty dang accurate. It’s hard to point you in a direction whenever the numbers of runoff/ppm’s aren’t known. What do you use for nutrients? What soil or coco are you growing in?
Looks like genetics to me. If it is, then it shouldn’t be a problem at all.
I thought so to but 2 of the plants doing it…weird nonetheless. What strain are these? Are they all the same seeds?
I questioned that too, but if they came from the same mother… The blotch pattern really looks genetic.
@Kingbk0807 are the spotted plants both the same strain?
Only thing I could find with those markings, but you dont have the twisted growth so much, but I agree you need a ph pen, I got a vivosun for like $15 it does the job.
Interesting stuff. A new malady to add to the catalog.
Do a internet search for “cannabis variegation”
Tobacco mosaic virus is possible but quite rare in cannabis.
