Did you happen to notice any signs of stress before you transplanted? Was the plant quite rootbound? I wonder about the possibility that it is now showing signs of previous suffering.
The spots look vaguely fungal to me and a treatment with Serenade (cheap at walmart or home dePOT) is not a bad idea.
If it's just a lower leaf or two and does not spread in the next day or so, it's probably from before. The color of the spots is too chocolatey to be potassium deficiency. I'm sorry that one has me stumped at the moment.
stinkyattic Reviewed by stinkyattic on . Dark Spots My wife just transplanted this strawberry cough and suddenly spots on leaves. Growing under CFLs 3-5500k and 1-3500k Same soil mix I use with all my plants. 80 deg f. 1 3" fan with louvered door 24/0 lighting Any Ideas? This happened like over night. At moment it seems to be only older leaves. There is also some tip burn. Rating: 5