That’s about 22,000 kcalories of stored energy over the course of about 120 days. Or about 183 kcals per day. That’s the equivalent of approx 20 grams of fat. My first suggestion is eat a little less during your daily eating window, spread it out longer or increase your exercise a bit. On the possibility that you’re simply taking in energy a little too fast to use it all before storage starts. Since you’re already eating to a caloric deficit, I’d recommend simply extending your eating window an hour or so. That may be all it takes to use those 180 kcals per day.
My second suggestion is try a different whey powder that doesn’t contain the additional stuff listed by Leanfit. It’s possible one of those ingredients is causing you problems, rather than the whey. AllMax Unflavoured ISONatural, for example, contains zero carbs and only additional sunflower lecithin. Shop around, you want pure whey, nothing else or as close as you can get.
Third suggestion. Weigh the stuff, don’t use ‘scoops’. A ‘scoop’ could vary by many grams depending how firmly packed you make it. And it’s virtually impossible to duplicate every time. So weigh it.
Fourth suggestion, since your problems seemed to start when you added the whey, back off on the amount of whey. I know you’re trying to build lean mass, but something is not working. I’d back off to a single ‘scoop’ - ie 30 grams. See what happens. For what it’s worth, which may be nothing, I eat 14 grams of whey daily in my morning keto coffee, 7 grams each of AllMax ISONatural unflavoured and PVL ISOGold ‘Vanilla Cream’ (which contains a lot of crap in addition to whey protein!). I’m likely going to drop the PVL when my current tub is finished and use AllMax exclusively. I bought the PVL for the vanilla flavour, but it’s not noticeable in the final coffee anyway.
Hope this helps. Maybe others with more experience will add their 2 cents.
PS: I forgot to ask what are you mixing the whey with? If it’s something other than water, that’s another potential problem, or not.