Decreased supply for no reason

So I have been a major over producer since my baby was born. I have donated over 10 gallons of milk and have a very large stash saved. About 2 weeks ago we notice baby was drinking more and had now started taking solids. She is 5 months old and is growing very well. However since this past weekend  I have noticed my supply decreasing. I pump the same schedule and breast feed on the same schedule I have been doing for several months. I changed my membrains for my pump and everything but still have a decreasing supply. I use to pump 15-18oz total when I woke up in the morning and today I only had 11oz and my pump at lunch time is usually 10oz total but today it was only 5.5oz total.