Answer: The drainage hole sounds as though it is an adequate size and if the pot is raised slightly above the water level in the tray, it should be okay. In fact, as the excess water evaporates, it should increase humidity near the plant. I really think at this point that the plant is trying to adapt to full sunshine. I suspect it was in a protected area in the garden center and the foliage just isn't ready for afternoon sunshine. If you can provide some temporary protection from hot afternoon sunshine, it should recover.
Best wishes with your strawberry guava!
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