My first post on the Astros was Astros Offense On Record Setting Low Pace. Right now their OPS is .630 and the league average is .727. So .630/.727 = .867. To convert that to a rate, we multiply it by 100. That would round off to 87. The last time any team had a relative OPS of less than 87 was in 1972, the Rangers, with an 86. Data from the Lee Sinins Complete Baseball Encyclopedia.
The Astros have an OPS+ of 70 according to Baseball Reference. It takes park effects into effect as well as the league average (it is calculated a little differently than above). The lowest team OPS+ I found going all the way back to 1920 was 69 for the 1920 Philadelphia A's. So the Astros are close to that.
The Blue Jays have an isolated power (ISO) of .206 since their SLG is .445 and their AVG is .239. That is higher than the all-time record of .204 by the 1997 Mariners. Relative to the league average, it would be the third highest since 1900, at 141 (.206/.146 = 1.41). The league ISO in the AL this year is .146. The 1927 Yankees are the highest at 153. My first post on this was Blue Jays On Record Power Pace.