Cool. The big filters aren't there to reduce the nitrates they are from a bigger tank that is now out of commission.. my tank is not heavily stocked and I gravel vacuum it twice a week to get rid of the fish waste. I have concluded that it's not HITH as it already has started to heal up since I made the post. Thanks for your input though.
If the OP just did a water change, 5ppm nitrate may not be low.
I try to keep my nitrate level between 2-5 pp by doing every other day water changes.
But to the question, they could be scrapes.
I blow one of the shots up a litlle, but it washed it out a little.
Problem with scrapes like that, is they are a perfect entry point for HTH to take hold.