ᐅ Regrouted the paving slabs, but it looks messy now.

Hi, the joints of the paving slabs in the entrance area were partially washed out and have been renewed. Fugli paving joint mortar was used, but the work was done poorly. It appears that while sweeping in the mortar, a wet broom was wiped over the concrete stones in some areas.

Now, after a few days and even after rain, the paving slabs show gray-white discolorations, partly covering large areas. Washing with water did not change anything.

What can be done, and which cleaner should be used? Thanks for your help.