T Tauri stars are young dynamic objects experiencing accretion from a circumstellar disc. This is a stochastic process so changes over time are normal. An inverse P-Cygni profile is a signature of infalling material which is part of the accretion process. However accretion is not continuous and tends to happen irregularly so it is not really surprising if the inverse P-Cygni profiles come and go in the spectrum. It would be interesting to take further spectra periodically to see how they change. Changes in accretion may also manifest themselves as changes in the magnitude of the star as it brightens and then fades.