Wow 4' in a 1 1/2 gallon bucket? And here I was worried that my 3 gallon buckets might not be big enough... Move up to a bigger pot and I guarantee you won't be disappointed with the results. Furthermore, those do sound like pH issue. pH is difficult to control when the pot is too small for the plant. You will face sings up and down and eventually you will face lockout. Anyway, it will be interesting to watch. I hope you prove me wrong!