All 89 bee plants
Red deadnettle pollen
Lamium purpureum
Orange red to brick, in the red range.
FloweringMarch to October
PollenFair
NectarYes
SeasonSpring, Summer, Autumn
WhereGarden, Farmland, Waste and verge
Long season on any patch of disturbed ground.

Easy to mistake for these
Closest pollen colours in our set, measured the same way the pollen identifier scores a match. Colour alone will not settle it, so check the flowering months and what is actually growing near your hives.
Out at about the same time
Saw a load like this going in?
Sample the colour against all 89 plants, then keep a forage record per hive.