Yep, defo too much water. I find Tabac one of the easiest soaps to build a lather with my hard water as it doesn't need much hydration.
Id try going back to basics. Soak your brush then flick off excess water so it's damp. I find 10 seconds loading is enough for a 3 passes if I so wish, then start building your lather, keep going it may take longer than other soaps, if needed just dip the tips in to add more water.
A good tip to see whether a lather is hydrated enough is to get some on your finger and gently swirl it in some water, if it dissipates easily your spot on, if it doesn't dissipate it needs more water and if just slides off your finger it's too runny.

Hope this helps