Temp dip 2 days after ovulation?

This is my chart...I'm very regular and ovulate on either cd18 or 19 per ewcm and OPKs. I have a hard time catching my LH surge and didn't have any positive opks but had a very close one the morning of the 21st. I'm concerned I didn't ovulate when I thought...which really wouldn't make any sense. This is my first time temping so I don't have anything to compare it to. Has this happened to anyone?