From reading, I was originally going to say they are most likely stretching for light, and need to be placed heigher up in the tank.
Pic was small, but I have another more likely possibility. Looks like they are getting good light (judging by the others around the frag). Looks to me like they are crowding each other on the frag plug/rock they are on. Looks like they are crowded and reaching for light due to the crowdedness, and not the need for more light.
After a zoa frag fills its space, its fairly common for them to crowd out, before moving on/reaching for another rock to grow on. They will most likely start reaching/spreading to new real estate soon, on your surrounding rocks.
If they have been in that spot in the tank for a while, and have been growing well, I would leave them where they are at. They look like they are happy and growing well. Moving them will only interupt the good they have going in that spot.
