This is interesting. It sounds like you used the proper stage of flower/bud. Did you make the infusion with fresh flowers or dry them out first? Is there a lid on the jar? Did you use the same amount of oil to St. Johns wort as previous times? Is one of your infusions redder than the other?
It may be that it will fully release those red oils once closer to the 4-6 week mark since sun method is just not as fast as the crock pot of course. Another thing you could do is mash the buds/flowers to support the release of those red oils.