Well, for a soil grow, a pH of 5.5 is far too acidic to start off with here... your ideal pH is 6.2-6.3 but anywhere between 6.0 and 6.5 (some would say 6.8) is good. I think you've got the start of a calcium deficiency or some OTHER deficiency and that's probably the result of your pH issues... calcium and magnesium cannot be absorbed if the pH is lower than 6.0, phosphorus requires 6.2 minimum, so to get this lady back on track, I would focus on pH...
Good luck!