C.K.
I have a 10 month old who also slept fairly well until 8 months. It is because around this age kids learn about object permanence (things i.e mom and dad are still there even though they left the room. We tried rocking, breastfeeding, singing, etc...stil upset. Tried pick up, put down. Tried modified ferberizing. We finally let her cry for up to 30 mins. Took a week but now we put her down drowsy after rocking and 2 songs. She falls asleep within 5 min with little crying. Consistency is key, so whatever method you pick stick with it. All methods fail if they are not consistent.