If just red stems, it may not be normal.. there are some red phenotypes, but you have to look at all of the plant characteristics before you can safely assume that red stem is pure pheno, and not an N, P, K, or Mg def. The yellowing points to the start of N def, as well. What type of soil is it? (pre-mix or custom? manufacturer if pre-mix? recipe if custom?) Have you done a pH check? When was the last time they saw water?