The first crop is always the biggest as it is grown at its peak with all the nutrients in the bag available.
Each successive crop gets smaller as more nutrients and water are extracted from the kit. Soaking overnight between crops and misting well can help to mitigate the moisture loss, but the nutrients will slowly run out, producing smaller crops over time.
Your second crop will start to grow in around 7-14 days, but can occasionally take up to 21 days.
Once you have had at least 2 crops from it, it’s worth trying to re-soak and get another, but if you do this and no further crops emerge after 4 weeks, then it is time to break up the mixture that is left and add this rich soil amendment to your plants!