Has anyone ever seen this on their tomato leaves?

Does anyone know how to fix it?

Hopefully extraneous variables:

- These are the 'early girl' variety.

- 2 weeks before I noticed these welts, I took this forum's advice and bought an EC meter. Finding that I was drastically underfeeding them, I doubled the concentration of the nutrient solution. (Shock?)

- I switched from 400W MH to 400W HPS for a week to see if I could force it to flower. It didn't, and these welts appeared on all tomato plants in the room during that time. No welts on my greenhouse tomato plants, and I'm notoriously poor at keeping things sterile. I switched back to MH because it's in our closet, and HPS is an UGLY light.

- I was misting them daily, and the places where these welts were worst was where the leaves would not quickly dry (towards the bottom). I have since stopped misting.

- The main tomato plant with the welts is 4' tall and 80 days old. The others are much younger, but the welts are less pronounced.