Based off of the abilities each Knight has it looks like everyone is getting, at a bare minimum, +263% attack, +20% crit rate, +30% crit damage, +15% damage to bosses and +15% skill damage for the whole squad. Everyone except for Hyacinth gets self-targeted bonuses of +50% crit rate and either +100% (Yarrow) or +150% (Diamond Frost, Rainbow Rose, Balsam) crit damage so they're set to output a lot of damage when skills go off. Thanks to 1.65x skill proc from Diamond Frost (first round only) and 1.2x from both R Rose and Yarrow there's a decent chance of those skills going off too.

As for the FMs, I'm guessing at least one of them is the Red Spider Lily FM (adds the ability to hit slash weaknesses for the wearer and one squad member when max level is capped at 50, self-targeted otherwise) since it looks like all five Knights were dealing super crits.