When I add gel or soft paste food coloring to my royal icing, it won’t fully mix. There’s white streaks throughout the icing no matter how much I stir. I’ve mixed hundreds of batches of royal icing with the same recipe and brands of ingredients and never had this issue! I’ve tried making new batches of icing using a new batch of meringue powder, cleaned everything with vinegar, used thicker consistencies, added more meringue powder . . . nothing has solved this issue, HELP!