I started to worry a bit. My gorgeous plant starts...

Well its a combination of 2 things . Firstly you need to add a bit more PK 0.5 ml isnt strong enough at this age and stage of flowering . How ever over time when your plant starts to ripen and get closer to its final days the leaves will also start turning yellow . At this point I would just add a little more of your Bio-bloom I would go 1.5 ml / L this way you can ensure your plant will get what it needs in the final weeks of growth and you will see that yellowing slow down until the end of your grow when your plant is really sucking up all the nutrients it can and your flushing the medium to get rid of the chemical based nutrients you been giving your plant . I hope this information helps shed light into your situation and explains the very easy way to fix this slight problem your having by adjusting your nutrient solution . -Happy Growing!