Weight loss journey - bad week weight wise

Starting weight (25 May 2018 = 273lb)
Today’s weight = 181.2lb
Average weight last week = 179.6lb
Average weight this week = 180.0lb
Weight gain this week =+0.4lb
Note: I weigh every day first thing and calculate weight loss based on average weight for the week.

Not a good week for me in terms of weight loss as I have actually gained 0.4lb. In terms of weight it appears as if I have hit a brick wall . An overall standstill with weight this week the same as it was 3 weeks ago. My weight difference between today and yesterday did not help with gain of 2 pounds overnight. Can’t understand or explain why since there was no excesses in terms of diet - it’s next weekend I am out for Veronica’s Birthday meal