Another I recommend trying is ensuring any indoor daytime lighting you use is broad spectrum (not just a [edit] cool [/edit] temperature).

Also on this subject, John Ott's books on light are a great read. In the 50s he was doing time-lapse films of plants for Disney and as he noticed his plants growing and blooming differently under different light, became basically obsessed, expanded his experiments to humans and cells and pushed an agenda of light quality that few wanted to hear the rest of his life.