I am pretty sure that you never thought of the following question but you cannot imagine how much thinking I wasted on it.
The following facts are true about the following vebs:
1. заботиться + о + предложный падеж
2. ухаживать + за + творительный
Let's now consider that the two verbs are put together in one preposition (perhaps it doesn't make too much sense but is for the sake of the example):
1. Я хочу заботиться и ухаживать за тобой
2. Я хочу ухаживать и заботитьтся о тебе
Conlusion: The noun should agree with the second verb. Correct?