My 8 weeks old kitten is a fussy eater..?

From the day one she eat very little few times a day i have kept dry food (Royal Canin) and i also give her wet food like 3-4 times a days table spoon full and i also sprinkle dry food on it>>she will only eat half of that..Today she got dierreah and she only licked the gravy and eat very little from her bowl but she drank loads of water...How can i make her a good eater. About her dierreah there is a separate question...thanks