m0useanswered grow question 3 years ago FFOF is a soil based growing medium be careful of getting ph below 6.2. ideal soil range ph is 6.5-6.8 and lower is for when your growing in soilless.
It looks to me like a PH swing. you will need to fortify your medium with some nutrients as well, FFOF if good but not a start till end option. make sure your feed has all the macros and micros your plant will be needing.
add silica first, then CaMg then the others. Give them a good stir and wait between adding them. Only ph balance after the fact.
Good Luck!