It didn't drop far, so it's not far off... try to raise pH a bit more i think it's fine.
Get that to 6.5-6.8 and see how that impacts the chemistry of all th evarious nutes invovled, then adjust concentration and or ratios of what you feed after you find some stability.
adding stuff before you are certain only makes you feel better. Don't let that impulse be a reason. Find a cause...
life works on cause and effect.