The question feels like it needs a reason. What it actually needs first is a measurement.
A drop is only information against a baseline, and the baseline is sitting in your thread.
Free to try. We never store your chats.
Replies got shorter — compared to what? If he has always written in 3 words, 3 words today is not a drop.
The useful comparison is him 2 months ago against him this week, not him against anyone else.
A cliff. Fine, then nothing, from a specific day. Something happened, and it is usually findable — look at the last exchange before the edge.
A slope. Slightly less each week for a month. Nothing happened. This is the shape of drifting, and it is the one people misread as a fight they cannot remember.
A dip. Down for 10 days, then back. This has usually happened before, and what ended it last time matters more than why it started.
Something in his life got heavy and texting was the first thing to go. Interest cooled and he has not said so. Or he is waiting on something from you and you did not know it was your turn.
The third one is more common than it sounds, and it is the only one of the 3 where a message from you fixes it today.
If it is a cliff, do not ask what happened. Ask about the specific thing, if you know what it is.
If it is a slope, a heavy message will not reverse it. Something small and easy will do more.
If he asked for space or ended it, this is a different situation and a message is not the move.
Paste the thread and it reads this week against the months before it — what he was like before, what has been changing lately, and whether this is new for him or just how he is.
Then it tells you whether to send anything, and writes it in your voice.
Try it on your conversation