What hardener did you use? If you used the 205 or 206, this may be blush that was not removed. Even with 207 special coating, it is always a good idea to clean before re-coating. The other thing might be air trapped in the mix if you overworked the mix either with a roller or with your squeegie. This type of thing often happens over a long period of exposure to sunlight, moisture and the elements, but should not happen in 5 months while being stored in your basement.