Baby food and gas

Really hoping someone can relate or give me some insight! My little girl is 6 months almost 7 and ever since we started her on baby food she is so gassy. Only at night though, she'll wake up screaming so bad for a good while and her stomach is so tight. We give her the baby food around 5:30 pm and she goes to sleep typically around 9:30 - 10:00. We've tried gerber, and beech nut naturals. We have spaced the different foods apart, like green beans for a week and then peas, etc. it doesn't matter what we give her, she won't sleep at night because of the gas. Gas drops do help eventually but I'm looking to prevent the gas, not continue to give her gas drops multiple times a night. I understand that transitioning to baby food can be tough on their stomach but I really don't think it should be this bad. She's a completely different baby since we've starred the baby food.  Is it possible her digestive system isn't ready for solids yet? She was born at 36 weeks. Her pediatrician doesn't seem too concerned, she advised us to avoid the foods that are causing the gas at her 6 month weakness check up, but that's all foods! Last night we did not give her baby food and she slept soundly with no gas pains. Help??!!