I need advice

If it was a deficiency, many if not all leaves would show symptoms. Plant looks quite over fed in general, so I doubt it is missing anything much. Damage does look the leaf was resting on the soil surface, most probably at night when the plant lowers its leaves. It is not a calcium issue. Too much cal/mag can have a negative impact.

Does that leaf touch or get very close to the soil? That could be the cause if it does not progress beyond that. your soil is listed as peat, perlite and vermiculite. If this is mostly unamended, it's soilless. If giving 100+ ppm of Ca, you are probably fine... if it is soilless, are you religiously getting 10% runoff minimum? This is how you avoid buildup. Also, remember runoff readings and soil slurry readings are not precise. They will differ from what is actually happening in the medium. It's useful info only if you have a baseline of what is normal for healthy, problem-free growing. Leaf looks like it was resting on the medium. That's probably the cause as what can be seen otherwise looks healthy. Even being very close to the medium can mess with the leaf - micro climate of that 1 leaf tip.

Don't think you are reading EC values correctly, need to supply the units of measure you are using. Lower soil pH accelerates the rate at which dolomite lime releases calcium. This is because the acidic environment in the soil promotes the dissolution of the lime, which is composed of calcium and magnesium carbonates. EC in water is measured in mS/cm or uS/cm. EC in soil is measured (dS/m). The amount of electrical conductivity (EC) a soil can handle varies based on the specific plant, but generally, most cannabis plants can tolerate EC levels between 0.3 and 1.8 dS/m. Unless you are making the conversions and doing the math, numbers mean nothing without units. Anyway I don't see any signs of osmotic damage that comes with salts in the medium, just a little blip of calcium.

you don't have a diary so who knows. So 4 weeks of veg, how big is she. Show a pic of whole plant. Some issues start at the bottom, some top, some young leaves, some old leaves. Have no clue what your feeding her. What soil is used. Some soils doin't require feeding until week 3-4 and then only about 1/4 of recommended dose. They need a rounded out regiment of nutrients, both macro and micro their whole life just different quantities in veg then flower. Could be Zinc, cal/mag, phosphorous, temp and humidity imbalance. Good luck

Its not deficiency its that you have a soil full of salts you Need to give It a good flush With plenty of water and let It dry out complete and then Just pH water and After all that you can feed It egain with nutrients ❤️💪