Decrease in Milk Supply

Denise • Married - 35 - mom to a 3 year old girl & baby boy.
I work full-time and pump 3 times a day while at work. My mom watches my 6 month old while I'm at work. She let me know the baby is drinking about 4-5oz during each feeding. I'm able to pump 3 oz with my 1st pumping session, 1.5-2 oz with my 2nd session and 3rd session. I'm not pumping enough to keep her fed through out the day and we have started to supplement with formula when she's with grandma. I started taking 2 fenugreek capsules 3 times a day but have seen no change. I also started pumping at night before bed but I only get enough to make milk ice cubes for her rice cereal the next day. She has rice cereal twice a day and veggies for lunch. She's on the smaller side, weight wise. Any ideas on how I can increase my supply? We hada successful 6 months and I'm not ready to give up.