Too much?? And sooooore!!

Hello fellow Blenders!! I have a few questions and am hoping for some answers from this wonderful community that I have been stalking (but never posting). :)

I have been working out with FB for the last year and a half, steadily increasing my workout minutes and intensity. I'd say for almost a year I have been working out 6 days a week for 45-50 minutes a day. My routine is below.

Monday - Upper body strength

Tuesday - 10-minute abs and HIIT

Wednesday - Lower body strength

Thursday - Rest

Friday - Upper body strength

Saturday - 10-minute abs and HIIT

Sunday - Lower body strength

About a month ago I realized I couldn't go quite as hard in HIIT and was tired pretty quickly when doing strength and after reading a bunch of posts on here I decided to take a week off. I hadn't taken any (extended) time off (minus my one rest day) for the entire year and a half.

After the week off, I decided to purchase a program and see how that worked. I felt my core needed some work. I purchased FB Abs Round 2 after reading a bunch of reviews and I am happy with it! So after the first 2/3 days of FB Abs (I'm only on the second week) I was SO SORE. Like, I haven't felt this soreness in a LOOOOOONG time. And all I could think was does only a WEEK OFF and then starting again cause this much soreness? That doesn't seem right at all! How could I be this sore when I did much more difficult strength and HIIT sessions for so long??? Any thoughts on this?

Of course I recognize why my core was sore...my core is NOT strong, as I've been learning!! But my legs are like steel (as another member said, haha) and my arms have definitely gained muscle.

My second question is about my schedule above. Is that too much? I've read tons of articles on over training as well as taking time off but you all seem really knowledgeable so I thought I'd throw it out to you guys even though I made sure to spend time educating myself first. I know I don't have much cardio in there but as Kelli says, those strength sessions quickly turn into cardio!

Sorry this is so much but like I said, I've been stalking this community and while I did my own research, I feel like the community could be so helpful, especially with personal experience.

Thanks so much!!