Have I Permanently damaged my Bearded Dragon ?!?!?!?!?

I bought my beardie about a month ago and he is the coolest little guy ever but I'm afraid I've been keeping his tank way too cold (70F) he hasn't grown much at all since i got him he is about four or five inches. I've recently gone out and bought a fluorescent UVB bulb , a 75 watt heat lamp, and a basking rock for under the light please tell me if I've ruined his growth and if not what are all the best things i can do for my spikey friend?!?!?!