This is what we call "scorch". The inter-veinal spaces brown out because they are not getting enough moisture.  The photos are consistent of a tree that may have a compromised root system.  So yes, too much or too little could both be right. In your area several years ago, there was so much rainfall that we continue to see problems in areas that were soggy or wet.  The saturated soils led to root loss, which in turn, do not allow the tree to get what it needs during the dry months.  Hence- scorch.  At this point, I would suggest you provide your tree with moisture during any prolonged drought.  And deeply too!  At the same time, don't augment natural rainfall in spring and fall when we are seeing a lot of it.  We have just had more than 5" of rainfall on top of a drought deficit of 7+".  They have had a good drink- so just be mindful of drought in July and August.