Did you try to remove the fertilizer granules, or was it a liquid feed? Leaching it out with lots of water might have helped if you had done it immediately, but the damage is probably already done at this point. I'd suggest moving them into a more shaded spot and see if they will recover. Damaged leaves are beyond help at this point, hopefully they'll push new growth and recover. Overwatering probably isn't a concern if the planting mix is well drained given that your ambient temperatures won't lead to rotting out of roots with frequent watering. Don't let the soil sit in a saucer with standing water, however, as you could potentially rot out the roots after dividing it.