Putting more weight on the bar

Before I came to LFRV I was a reasonably strong lifter. I was also suffering from some form of chronic fatigue and found it hard to get out of bed most days. But even through the worst of it, on my old diet (which was your typical omnivorous high protein lifting diet), when I did manage to get to the gym (about once a week) I managed to at least maintain my strength and over a long period actually increase my lifts.

Since coming to LFRV (six weeks 100% now) I feel about 1000% better, have energy all the time and loving life. No desire to go back whatsoever. And I'm back at the gym, and training a sensible 3 days a week, with some cardio on the off days. But despite training efforts, my lifts are decreasing. Yes, I'm training properly and recovering even better, but still facing strength loss. Every time I go back to the gym I can lift less than the last time.

Help?

More information: Didn't have any transition issues, because I'd been following DR for some time on YT and just followed his advice 100%. Liters of water, 3000 Cal minimum, 10 hours sleep, and ripe, watery fruit. Transitioned over night, very few cravings, and only twice did I run out of food, the first time I was at work and they were shouting pizza so I partook (ow) and the second time I just had some plain rice and plain boiled potatoes. When I started I was managing about 2900 Cal, have increased to the point where I am hitting 3500 every day, ALWAYS aiming for more, but the most I've ever packed in was 4300 in a day. Finding it hard to get more than that. About 80% of the days were logged on cronometer, getting better at keeping that logged every day. Didn't weigh myself over the weeks, but at day one I was 88kg, and after four weeks I was 81kg (about 5'11"), so that would be water plus some biomass lost. Cardio fitness has increased from poor to average in this time. I cycle everywhere.

Completely expecting the answer to be: eat 6000 cal instead. But how is that even possible? Dried dates in datorade or banana/date smoothie can give me the melonbelly easily, so I'm doing that only twice a day instead of more often. Outside of that, my mainstay has been oranges so far. Ripe and delicious mangos are hard to come by here, unless you want to pay about $7 each (I can get ecuador mangoes for about $1.50 each, but theyre almost always unripe and they never seem to ripen after purchase). It's early summer here if that helps. Any tidbits appreciated. Thanks.