They are filling up pretty fast i always try with this method, but no i didnt feel any heat. Maybe the problem is in cal mag...When I see what your plants looked like one month ago and where there at now its amazing how fast they grew and budded. I have never heard of Dutch Passion before so I don't want to advise. All I do to test light intensity is pretty caveman. I just let it shine on my underside forearm for a few minutes to see if I feel a burn and guesstamate from there. How are ya on the calcium and magnesium ?