Growth looks like it's stopped, is it time to flush?

No need to flush, they fatten up the most in the last week unless you wash away the nutes, but its up to you. They look good, when they fatten up more will look even better. Use a soft measuring tape and check measurement now then do so again next week. Or take 1 picture at one distance, then don't move the plant and do the same at the exact same distance next week, and watch for growth. Its easier to notice with 1 week apart photos from the exact same location and aiming at the plant from the same angle.