Why am i gaining weight when I’m 100% following protocol?

Hi! I’ve been on protocol for 3 weeks. I went from 160 to 151 over the last 3 weeks. I’m planning meals a day ahead and have perfectly followed plan. I do intermittent fasting from 6pm till 9am. I walk 4 miles a day and cycle on Peleton 4 times a week. My daily plan is pretty standard…2 eggs, Ezekial toast and avocado at 9, raw veggies with full fat dressing at noon and meat/cheese/veggies for dinner at 5. Despite this perfection I gained 1.5 pounds yesterday instead of continuing to lose. I haven’t been counting calories but with the gain yesterday i added them up and it was only 1100kCal. Why am i gaining on this diet? Is there something wrong here?