here is a second photograph to help you see it better

I would surmise that it is something cultural going on.

Too much/too little light, food, water, inconsistent temperature, water droplets on the leaves, lack of humidity, etc.

Shouldn't be anything of great concern, ... unless you are growing to show (i.e. compete).

Over watering, too much fertilizer, water that has chlorine in it. Since you have had the plant for four months and this is a recent occurrence I think over watering can be ruled out unless you have changed how you do that lately. Had it been that you probably would have seen signs before now. Try not fertilizing for a bit. It is always a good idea to start a leaf of any plant you value imho. So you always have a back up. Not to mention the shear joy of "I did that". I don't think the this plant is in mortal danger. Just won't be pretty, for awhile. I could be wrong. Have been before. It's a learning process for all of us.

Aha - I looked around - and the list is long - and they all look the same - sunscald, drafty window, too cold, cold water used for watering, cold water drops on the leaves - and there is one I didn't hear before - zinc deficiency.

Anyway - I have a plant - Santpaulia confusa - that grows like a moppy weed it is, blooms all the time - annd always develops yellow spots with yellow veins. What it wants - I do not know - and it doesn't pass this spotting t the neighbours.

You have your plant for several months - and leaves live for a year - so if there were some unlucky curcumstances to damage the leaves - the plant will grow out of it.

I.