Bbt interpretation?

I have read you can have a secondary estrogen spike in the luteal phase and for me that occured on cd21 last cycle (but i didnt test on cd20).

And now on cycle day 20 (which according to this and ff is 4dpo, but femometer is 7dpo) has anyone had this? It makes sense if it is estrogen my temp has come back up.

(Temp is back above coverline but i screenshot before glow updated and i dont want to go out of my post here)