Help! Brown Leaves!

My vinca are starting to bloom, but some of the leaves are looking terrible. Am I over watering, over fertilizing, under watering, under fertilizing, hardening off too quickly??? Help!

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It looks a bit like sunburn to me. If you haven't gradually accustomed them to the amount of sun they're getting that can happen--even bright light indoors is nowhere near as intense as real sunlight.

Is sunburn something that they can recover from?

Those particular leaves won't go back to being green, but if you don't get any more sunburn than is there now then the plants shouldn't die and any new growth that forms should have a normal green color. With the leaves that have been damaged, you will probably find that they continue to look worse--the sun damage kills cells in the bleached looking areas, so eventually those leaves or parts of leaves will probably turn brown so don't worry if you see that happen.