Little yellow leaf on top

It is nothing, you are over thinking things. Calcium deficiency will show as brown spots/dots.

I think these are burns from the fertilizer, nothing bad, next time just use a little bit less fertilizer. That was with me this week too! Otherwise it looks very good, you have a beautiful plant.

Salt build up or high nutrient content looks to be the culprit maybe cut back on the strength of your solution Mate

The plants show the pH problem through the tips of the leaves. I read in your diary that the pH is 5.5. It's the second week of vegetation, I would raise it to 5.8. It doesn't look that bad anyway. Just fix that little detail.

@Grave77 I think it's a light burn from a liquid sprinkled on a leaf tip

It’s looking like you might be running your nutrients a tad bit hot for that stage of life. Make sure you are testing PPM to aim for roughly 350-500 PPM in the early stages of your plant. The older the plant gets and the more growing it does the higher the PPM will be to support it. I hope this helps.

Yeah, it's probably not calcium deficiency. More likely, it's nutrient burn. Check your feeding routine. Make sure you're not overloading them with nutrients. Keep an eye on your babies and adjust as needed. They'll bounce back, man. Happy growing! 🌿🔥