Hai mama! Berat 6kg at 7-8 months memang on the lighter side, so kena check dengan doctor dulu to make sure baby okay and what he specifically needs, sometimes it's just genetics, sometimes perlu adjustment in feeding. A few of us mum friends noticed our babies gained better when kami ensure proper latch if breastfeeding, or kalau formula, make sure the ratio of powder to water is correct and baby drinking enough throughout the day (jarang-jarang ada formula yang "magically" boost weight, mostly about quantity and consistency la). Suggestion ko tanya pediatrician pasal best formula for baby's needs dan maybe anak ko kena top-up or switch, because every baby different dan doctor will know what's suitable for your little one. Hang in there, mama, first time memang stress but you're doing great!