So yeah, dark green leaves are usually an indicator of too much nitrogen. Those leaves are a little dark, but honestly don't seem too terribly dark to the point that I would worry a ton about it. You don't seem to have any leaves clawing which is another sign of too much nitrogen. The plants do still need a little nitrogen throughout flower, so you shouldn't 100% cut all sources of nitrogen.
I couldn't find any NPK values for the Bio-bloom you are using, but it seems like it may only contain Phosphorus and Potassium. Looking at the biobizz feeding schedule, they feed their grow nutrient throughout the whole grow, so that backs up that the Bio-bloom doesn't have any nitrogen in it. So I deff wouldn't stop adding your grow nutrient. Maybe just dial it back by half and see how things go.
Its also entirely possible that the genetics of that plant are prone to growing darker green leaves. If the plant has always been a somewhat darker green that may just be the case.
I wouldn't necessarily recommend doing a flush as this point like the other guy mentioned as the plants do still look fairly healthy. I would just start by backing off on the grow nute and see what happens over the next week or so.
Good luck! If you need any more help or advice feel free to dm me!