Yellow leaves/Brown spots on leaves

Hi there The yellow tips on the new growth looks like neut burn .. The first bottom two leaves I wouldn’t even worry about, The look rich in nitrogen from overfeeding.. They will need watering more frequently the bigger they get, I would just use water for a day then cut down the neuts abit make sure you’re using the correct dosage, Best of luck 🌱

Cotyledons can die off at any time, that rusty spot, could be fist sign of calcium uptake issue, most probably ir is blocked by excess of nitrogen. why i say so ? new growth is slow and solid green, plant is stunt a bit. would not panic at all, but just would go few plain waterings , without adding any food. Happy Growing !!!