The yellowing looks like it is marginal meaning on the exterior edges of the leaves which does suggest a lack of water or scorch given how hot it's been. Since you think they get enough water, you might check that they aren't getting too much water because symptoms can be similar - although given how hot and dry it has been since mid-June, it seems more likely it is underwatering not overwatering. Remember that our humidity has been in single digits some of this summer and that causes heat stress.