First leaves died. Overwatering?

Yes, your theory is definitely plausible. Overwatering is one of the most common mistakes for beginners, and it often leads to root suffocation, which manifests as dying leaf tips and yellowing because the plant can no longer take up nutrients properly. When the roots are constantly drowning, they start to rot, and the first true leaves are usually the first to show the stress. However, since you mentioned the dying started specifically from the tips, you should also consider nutrient burn if your soil is too heavily pre-fertilized for a young seedling, or even underwatering if the roots haven't spread out enough yet. I'd highly recommend checking how heavy the pot feels before you water next time and ensuring you let the top layer of soil dry out completely to give those roots some much-needed oxygen. Happy Growing Growmie🌱