All aesculus species - horse chestnuts and buckeyes - are subject to a number of leaf infections which show up as spots or blotches. These usually appear later in the growing season, but some appear earlier under the right conditions. The specific pathogen really can't be determined from a photo, so your extension service is your best source for determining what you are dealing with. In most cases, however, aesculus leaf infections are more aesthetic problems than a lethal threat to the plant. None of this has, imho, anything to do with the bricks or unidentified stress.