My corn plant is not doing so well and im not sure whats happening. I havent watered it in 2 weeks for fear of over watering. But i think it might be something else. I have been using tap water but i would sit it out for a day or two before use. I plant to switch to rain water for next watering. The leaves also look like they are drying out. As if they were ashy

Any ideas on what i can do?

The leaf spots are far and few between and not a cause for any corrective action.

If your tap water is hard, letting it sit overnight will not help. Use filtered or distilled instead. Chlorine and fluoride in tap water are not harmful to plants.

Are you having a fungus gnat problem?