The Foxes struggled to match the visitors on the day as Emile Smith Rowe and Adama Traore struck for Fulham.
Justin said afterwards: "It is frustrating. It has been a shocking run from us. We're trying to do everything to change it but nothing seems to be working. We are deflated. We'll have a couple of days off and then regroup and see where we can improve."
On fans booing, he continued: "They pay their money to watch their club and we're not doing the club any good at the moment. They can boo if they want to be honest. They are entitled to do that. It doesn't help anything I don't think, but we're the ones getting them there at the minute so we need to do something to change that.
"To put our finger on it is hard to be honest. We just got caught at the start of the second half and we've done that a few times recently to be honest. We tried to do a professional job, particularly in the first half, but to go out in the second half and concede from a nothing throw in is really disappointing and something we need to look at.
"When we take a step back and analyse the game we'll see what we did well after their goal and see if we can build on that and improve, but at the end of the day we've conceded another two goals and not scored so something obviously has to spark in the group and staff to get us going.
"Anyone with eyes who looks at the league table can see we're struggling with form at the moment. It is up to us within the building and training ground every day to do something and get out of this rut that we're in. We need to be better but the Premier League is difficult and you need to take every game as it comes and just play the match in front of you."