Ideas what these blisters are?
 

This orchid was a rescue from a large, extremely stressed mature plant that was abandoned outside an office. I was not going to take it, but after a month of watching the plant carefully, withering away, there was no evidence of pests or virus so I broke down and put the only remaining living piece in an isolated area. The plant was cleaned of dead roots/debris, washed, flushed with Physan 20, and repotted. After a little over month its growing very well.

Anyway, I noticed what look like blisters on its growing leaf. No pests are on the plant, and no pests get flushed out during periodic heavy watering. Ideas what these blisters are? Maybe residual damage to the leave from before I took it over – visible now because it’s growing? Sunburn?

The pics were taken after watering, the blisters are not water drops.

Good save! I have seen "bumps" like that on plants occasionally, don't know what they are but they don't seem to spread or hurt anything.