Bay Tree Turning Yellow

I have a large laurel tree which I kept outdoors all summer. I brought it inside and now the leaves seem to be turning yellow and falling off. I do not have the best light, but it is not bad. I put a grow light on the tree from 5:00 p.m. to 10:00 p.m.
Last winter I lived in another house and the tree had better light, but it also had scale. I had used something I got at the gardening shop, but it didn't work. My son-in-law suggest that I use a vinegar and water solution, which I did all summer. I think that I have gotten rid of the scale.

I had never heard of the vinegar and water remedy for scale insects. It sounds very organic! The important thing to getting rid of scale without using dangerous systemic insecticides is to remove the crawler stage as it hatches from underneath the dead adults. Since they hatch over a long period of time, persistance is very important.. Soapy water will do the trick too, especially if you use insecticidal soap.
Are you sure that the vinegar baths have not turned the soil too acid? You might try repotting since that would also replenish nutrients that the vinegar might have leached out of the soil.
Also if the light seems low still, I would put the grow light on for 14 hours and let it augment the natural light. Also make sure the tree is in a cool spot otherwise its metabolic processes use up more energy than the leaves can fix with the low light. This would make the plant drop leaves too.