You say you're using bloom nutrients - are you using veg/grow nutrients too? As the problem, I believe, is lack of nitrogen - which is found in veg nutes. I grow in soil and use Bio Bizz 'Grow' and 'Bloom' throughout the entire duration of the grow. I used to experience similar issues to you. After I started keeping both nutes going throughout, and added some 'Alg a Mix' (this is a seaweed extract and improves the organics of the soil) - I have found my plants are vivid green and totally healthy.
You also don't mention the ph of the nutrient solution you have been giving them. Anything to far away from 6.5ph and you are likely to experience problems.
But don't panic - they will grow out even if you loose most of the leaves. I had a 'Mad Shack' last grow that had major problems, lost all her leaves at about the same stage as you. I sorted out everything I have mentioned above - and she gained some nice dark green growth at the buds and finished up as the strongest plant. Keep the faith!