Blotchy grout

Tile pros - need some help. Over the past year, I've tiled about 3 different bathroom and kitchen floors - all using the Laticrete 1500 grout and polymer mix. As the subject implies, after the grout dries, it is blochy in areas. The latest project used one of their brown grouts. I have read up on this forum about efflorescence etc and that this could have occured from too much water in my sponge (even though I rung out the sponge thoroughly).

With this said, I'm wondering in the future if its just easier to use whatever grout I have and focus on grout colorants. For those of you that are pros - what do you do in these cases? I can't imagine that Bud, RD or Bill Vincent use grout colorants everytime. Any suggestions? Should I use something like a distilled water when rinsing the sponge? Any suggestions are appreciated, its just frustrating trying to get grout colorants each time.

Thanks

Rick