I recently bought a Hibiscus for a friend and I have custody of it until my friend moves into a new apartment. The leaves are turning yellow (almost on a daily basis). I am giving it water in the same amount as my own plants, but I have not repotted it and I am wondering if it is root bound. Can you please advise how to maintain green leaves and a healthy, vibrant plant? It blooms almost every day and I keep it close to the windows and it does receive at least 3 hours of intense sunshine. Please advise and thank you for your kindness.