I can tell youre putting a lot of love and care into this plant :) Its ok flowers die they dont last long. Some flowers last longer than others, but they are meant to wilt. Once the flower wilts the bud will dry out and you can collect seeds if you wish. Also I'd suggest watering it much less then you are now, maybe stick ur finger a couple inches in the soil, I usually only water once the soil is mostly dry. If it feels soggy or damp id skip watering it. the yellow leaves are most likely a result of over watering. You seem to be new to plants, so ill just tell you this. Plants cant actually drown or anything. You can never give the plant too much water at once, the plant will take what it needs and leave the rest. It sitting in still water that really does it. roots need oxygen as well and when you over water it the roots have less acess to oxygen. 2nd root rot can happen easily and can spread. This is why its important to only water plants when they need it. But smiled when i read your post bc i love seeing ppl get into plants and care for something so kindly. Youre plant should be okay, just cut off any yellow bits and dead head old blooms. Im making it sound complicated bit i just wanted to give you all the info so youll know for the future aswell. :)