Pat I'm not an expert, but I asked on here for my DLs, the leaves were doing about the same, only not so brown. Someone pointed me at spider mites, so I checked with a magnyfying lense the back of each leaves, and I did find some; also they chew the leaves and you can see little brown spots. If they are many the leaves suffers and get brown. You could check your DLs for spider mites. They seem to like hot and dry conditions. HTH
