Yellow spots on some leaves

The spots are pale and scattered, not the sharp, rusty or interveinal type you’d expect from a classic Cal or Mag deficiency. It’s more of a soft yellowing – could be minor root stress, light substrate imbalance, or just early adjustment to soft tap water. You can try a light CalMag dose as a precaution, but don’t treat it like a full-blown deficiency yet. Watch the new leaves – if they stay clean, you're in the clear.

Hi, yellow spots on cannabis leaves can have various causes. Common reasons are: Nutrient deficiency: A lack of nitrogen, potassium, or magnesium can cause yellow spots. Give them some CalMag as prevention; it can't hurt. I would only start giving the other nutrients from week 4 if your soil isn't sterile. pH imbalance: An incorrect pH level in the soil or water can affect nutrient uptake. You can check this by measuring the runoff; the pH should be between 5.8 and 6.5, and the EC value should be under 2. Pest infestation: Pests can leave yellow spots. Check if you maybe see small brown spots on the underside of the leaves, or those little fungus gnats. Light stress: Too much or too little light can damage the leaves. But it doesn't look like that's the case for you. Watering issues: Overwatering can also cause yellow spots, and in this case, the leaves are usually swollen and hanging down.

check your local water and make sure you dont have chloramine in your water. Chlorine damage and calcium deficiency look fairly similiar. i found out my water has chloramine in it so i have to boil and cool my water before use and it fixed the issues that looked like calcium deficiency for me. but to answer your question, yes it looks like cal mag issue but also check your water or make sure to dechlorinate your water