Since CT is veeeerrry busy these days because of all the seminars he gives, I’ll take the lead on the forum and back him up, so I hope it doesn’t upset you if I answer for him.
Ideally, on the 5 x 5, you try to keep the same weight for the 5 sets, This is why you need to keep each set at +/- 2 reps from failure. Now if you feel like you need to lower the weight during the subsequent sets, you may have too much weight for the 1st. Try starting lower. The idea is to create a neurological adaptation by lifting the same amount of weight for multiple sets.