Seeking Advice: How many failing students is too many?

Hi all, this is my first semester teaching a full load (5 courses total at 2 institutions) as an adjunct composition instructor. I taught 1-2 classes during my time in my MA program, and only failed an average of 3 students per class of 22. However, this semester I have 2 classes (both at a large-ish, public 4-year in the US) that are shaping up to have around 5 students failing, and at least one additional D (a grade that won't let them move up) in a similar sized class, and the other 3 will likely have between 3-4 Fs.

Despite having seen those grades dipping for a while, and reaching out to those students in turn, I am still simply flabbergasted at this outcome. I have tried my best to communicate thoroughly with my classes, prioritized in-class activities and work time, and utilized mandatory writing conferences, but so many students just stopped coming to class or turning in work around fall break. I believe my main failing this semester has been a backlog of final grades (I kept up with scaffolding feedback, but fell admittedly very behind on grading final essays), which has made this discovery even more abrupt. However, I also worry that my initially understanding and lenient approach toward absences and late work may have led students toward not caring about their work.

I'm sending out some last ditch communication to hopefully allow a student or two to resurrect their grade, but I don't have a ton of hope. Is this normal/average, or as terrible as I currently think it is? Am I simply not cut out for this job? How badly might this reflect on my ability to be rehired next fall? I would also highly appreciate any advice on how not to repeat this kind of a downfall next semester. Thank you in advance!