I am trying to grow Chlorella vulgaris but every time it turns grey with green particles at the bottom of the flash, or turns yellow ( the whole culture ). I use the BBM recipy that is written in UTEX with a pH of 6.5 - 7.2 ( i measured the pH of different cultures with media made in different times). I grow them in erlenmeyer flasks. In natural light ( i also use growth lights but nothing changed). Mixing in 130rpm and a foam top for air exchange.