I mix my mega crop the same way
I’ve experienced it yes my ph normally raises for the first couple days. Then seems to go steady. Not sure why
I have also noticed when I added kelp and Humic to the mix it balances and holds the ph better. Until I add molasses to the mix then it can go either way and I have no clue why
Last nights mix did not want to ph down after putting molasses in. It finally came down but took a bunch of ph down. I have had other batches of feed that when I add the molasses it drops below 5.5. Not sure if this helps or makes you more confused