my baby went thru that stage when she was a lil less than 6 months~~!! even when she was hungry she wudnt drink her milk, or wud just drink half of her normal amount... my mum said it was probly bcoz she was too hot - her entire head wud b covered w/ sweat after drinking the milk, so lost appetite, just like adults, when we're hot we lose our appetite, so we tried to feed her meal in 2 goes, we feed her n when she doesnt wanna drink anymore, we leave her to play for a while n after maybe half an hour we feed her again - sometimes she mite not drink all the milk but at least this way we know she's had a proper feed n wont be hungry too quickly. maybe u can try this method too...
after about 2 weeks she was fine again n was drinking her milk fine~~!! it'll pass, dun worry.