I read several places that for the fist submission, to limit the megapixels to the minimum required by each stock agency in order to reduce an initial rejection due to slightly soft focus or minor defects when submitting.  Well, my first batch of images have been accepted by Shutterstock, iStock, Fotolia, Dreamstime, and Alamy!   

Before I submit my second batch of photos, I hope to gain some wisdom regarding image size (megapixels).  Specifically, I am interested in your approach to sizing images for the five agencies listed above.

Thanks!

I just submitted my first photos to Shutterstock and three of the six submissions were accepted.  I am happy about that, but I have questions about two of the photos that were rejected (one is attached). 

Both of them were shot in my homemade light box and were rejected for "Poor Lighting--Image has exposure issues, unfavorable lighting conditions, and/or incorrect white balance" and "White Balance -- The incorrect white balance setting was used".  My light box is a fiberglass bathtub that I cut in half and painted with flat white latex paint.  The light source is a single 40w florescent bulb in a 16" galvanized metal reflector, with the light diffused by a white cotton t-shirt (I know, I know, but I live in a developing country in West Africa).  The photos were edited in Lightroom 6.

So, based on that, I have two questions:

1.  Is there anything I can do in Lightroom to rescue these photos?
2.  What do I need to change in my light box setup to improve my results and reduce post-production time in Lightroom?