Magnum grow

You should slow down with grow big and ALL nutes for few waterings, if you'll have excessive nitrogen it will cut off absorption of calcium. Normally it's aroun 0.5 ml/l if plants healthy and every feed watering only, not every time you give water. All the Best !

Yes, it looks like some of yours have started. They'll all eventual turn orange/brown then as the calyx swells and the flowers mature they'll start to recede back into the calyx.