should i end this friendship? but if i end this one i dont have any friends anymore. 21(f)

I’m a university student, and I have a friend group from high school. There are four of us in total (including me). Recently things got awkward between me and two of them.
Before this semester ended, I had separate phone calls with both of them, and we talked everything out. But I still feel kind of unsettled about it.
The first friend said she was really hurt that I barely replied to messages around December and January. The thing is, I was retaking my college entrance exam that year. I was at my art academy literally all day, every day because I was determined to make that my last attempt. I put all of my energy into preparing for the exam. I’d get home exhausted, shower, sleep, wake up, and go straight back to the academy. I barely had the energy to look at my phone.
She also brought up how I used to post depressing things on my Instagram story. She called me a few times after seeing those posts, but I didn’t answer. Honestly, I just didn’t know what to say, and I didn’t have the emotional energy to talk to anyone. She said that really hurt her too.
During our call, I explained everything, including my depression and the bullying I went through in middle school, and we technically resolved it. But I still don’t know how to feel.
The second friend was also upset that I didn’t reply to messages very often. She also said she was shocked because after I started university, I only reached out to her once to ask if she’d be interested in joining a group blind date. My university friends were looking for people, so I asked her.
The thing is, this confused me because we’ve never really texted each other casually. Neither of us has ever been the type to message first. We usually only text to make plans to meet up, so I genuinely didn’t understand why that specific message upset her so much.
Another thing both of them said was that ever since I started university, they feel like I don’t value our high school friend group as much anymore. They said our friend group is still their most important group of friends, but they don’t feel like I see it that way anymore.
What confuses me is that both of them went to good universities straight after high school. They made new friends, hung out with their classmates, and had their own university lives too. I, on the other hand, took an extra year because I was retaking the entrance exam, so I’m not sure why it’s such a problem that I’m also getting close to people at my university now.
Anyway, we talked everything through before the semester ended, but since then we haven’t talked at all. One of them actually sent me a message on Instagram, but I’d deleted the app, so I only saw it yesterday.
Now I’m wondering if I should reach out again.
It’s not that I’m desperately trying to go back to how things used to be. I just don’t want things to end on bad terms.
What would you do in my situation? Do you think I should message them again, or should I just leave things as they are?