Hey! First of all, I truly appreciate the fact that you are trying to improve yourself as a teacher and not blame them. I used to be a teacher for 8 years and I think I have some tips and tricks.

Communication: try to talk to them using the see think wonder method. That provides feedback to them in a way that is respectful and without blame. I see that you are talking when I am talking. I think something is wrong; either I am boring or the lesson isn't engaging enough. I wonder how I can help. Something like that. Be vulnerable and sincere, you'll be fine, just remember to use 'I' and not 'you'. You told us they're good students. So they must have good intentions.

Lesson plan: say you have 15 min of reading or 20 of explaining. Try to divide that into shorter stints with the appropriate follow-ups of course.. That keeps the flow going for them and doesn't give them time to wander off in their minds.

Hope this helps a bit! Good luck and remember we're all people who want a good connection.

This is a general teaching tip but it works especially well for ADHD brains. Try to use an interactive format even when it is you delivering necessary content. Rather than just delivering information, use leading questions to get them to work out the answer (or the broad outline of an answer) themselves. Then when you put up the slide with the answer confirming that they worked it out correctly all by themselves, they get a confidence boost and it makes the subject seem much less scary (and/or boring). It can help get the less confident members of the class contributing too, when they get into the swing of it.

Keep slides simple and interesting (pictures with short headers or questions are good) and back them up with a more technical/detailed handout (or worksheet if you have time for a practical) with links to further reading/resources. That way you can use the time to establish the understanding they need without trying to cover everything in too short a time, and they have resources to put the understanding to good use.

Don't be afraid of silences. Ask the question and wait until someone offers an answer. Make encouraging noises, coax them to the solution, but give them time to respond rather than panicking and moving on. Thinking time is good and they'll get into it.