Discouraging tactics - bad psychology
When I started today I was up to speed on all of the first set of topics apart from the last level of the genitive. Half an hour later after topping up 2 targets in the 2nd section I find that practically all of the first topics were down by at least 1 level. That's tantamount to saying the more you practise the more you forget - absurd!
I've always found the degrading tempo reasonable. The more times I strengthen a topic, the longer time it takes until it will degrade again. But it is a bit random; sometimes no topic will degrade for me in two days, and sometimes four topics degrades in the same day.
I don't know what might have happened to you. Maybe you just had bad luck today?
No-one seems to have read exactly what I said! I'm a languages teacher and wouldn't dream of dicouraging a student WHILE they are working hard! If I don't practise for a day or two fair enough, I expect to be docked a little here and there but not to come to the end of the session and find that I was FURTHER BEHIND THAN WHEN I STARTED!!
Three people have hypothesized a unique circumstance. The algorithms for calculating these things did, indeed, change for some users at a juncture very close to when you posted this thread. Certainly they ought to have introduced the changes more gradually, but they didn't, so now at least it's done and there won't be several recurrences as there might have been for a staged roll out.
If it happens again, different story, but degildings will happen. If many happen at once it could be because you learned (or quizzed out of) many at once.
What you describe sounds like a very rapid change that is, therefore, particularly likely to have been occasioned by the change in the algorithm. I had about 14 skills in the tree I was working on suddenly degild, too. This after having had only one degild in the previous four months.