Too much vitamin C??

After quitting smoking a few weeks ago (thank-heavens I am finally free of that revolting nicotine monster...) I have been taking a 300mg Vit C supplement to help restore levels in my body as I was under the impression that smoking prevents Vitamin C uptake. I have been taking them for 3 weeks now and my skin is becoming increasingly dry around my mouth, even though I drink about 4 litres of water a day and moisturise. Is it possible that the excessive levels of Vit C in the supplement are now preventing my body from absorbing other vitamins & minerals? I eat a low-dairy diet high in fresh fruit, raw veg and beans and pulses etc...if that helps in the dry skin diagnosis! Any advice would be great, thanks :)