Yeah there can be some warping. Nothing worth not having the plexiglass for, since plexiglass is cheaper than glass.
Are you resting the lights ON the plexiglass or just above it?
And I am glad your dielsiana has been transplanted less than two weeks. When you disturb the plant with transplanting it takes some time for the plant to get adjusted and growing and dewing up again. No worries about it.
Also, some older leaves will go brown, it is the growing new leaves going brown that would be any sign of concern. Most likely, in another week or so you will have some awesome growing dielsianas in there!