My first post on the Astros was Astros Offense On Record Setting Low Pace. Right now their OPS is .665 and the league average is .729. So .665/.729 = .912, giving them a relative OPS of about 91. That would put them in the bottom 25 since 1993.
If you have read my other posts on this, you might notice that the Astros have been doing better as the season has gone along. Here are their relative OPS figures each month this year starting with April:
.609/.735 = .829
.605/.726 = .833
.691/.720 = .960
.721/.731 = .986
.737/.728 = 1.01
The Astros have an OPS+ of 78 according to Baseball Reference. It takes park effects into effect as well as the league average (it is calculated a little differently than above). That is last in the NL this year. The Pirates are next lowest at 82. The lowest team OPS+ I found going all the way back to 1920 was 69 for the 1920 Philadelphia A's.
The Blue Jays have an isolated power (ISO) of .210 since their SLG is .460 and their AVG is .250. That is higher than the all-time record of .205 by the 1997 Mariners. Relative to the league average, it would be the third highest since 1900, at 142 (.210/.148 = 1.42). The league ISO in the AL this year is .148. The 1927 Yankees are the highest in relative ISO at 153. My first post on this was Blue Jays On Record Power Pace.