For the season their home offense has been significantly worse than the road offense. Personally I think they’re just trying way too hard to vaunt for the home crowd.
The Astros formerly hit better, scored more and won more in MMP than on the road. That has changed but the ballpark hasn't.
Well, the stadium
has changed at different times throughout the years. It's interesting to go back through past seasons and look for some correlation.
2018
Home: .244/.317/.395, 148 runs (on pace for 333 runs)
Away: .286/.353/.477, 246 runs (on pace for 498 runs)
2017 (CF brought in, new batter's eye)
Home: .279/.340/.472, 395 runs
Away: .284/.351/.483, 501 runs
2016 (LED lighting installed)
Home: .238/.311/.407, 334 runs
Away: .255/.326/.426, 390 runs
2015
Home: .253/.321/.462, 367 runs
Away: .247/.310/.413, 362 runs
2014
Home: .245/.315/.398, 318 runs
Away: .239/.304/.368, 311 runs
2008
Home: .272/.334/.443, 367 runs
Away: .254/.312/.389, 345 runs
2005
Home: .271/.340/.436, 360 runs
Away: .242/.306/.381, 333 runs
2004
Home: .277/.354/.453, 405 runs
Away: .257/.330/.420, 398 runs
2003
Home: .269/.346/.448, 425 runs
Away: .257/.327/.415, 380 runs
2001 (visitor's bullpen enclosed, HR line raised in LCF)
Home: .278/.353/.471, 440 runs
Away: .265/.341/.432, 407 runs
2000
Home: .280/.366/.506, 505 runs
Away: .275/.355/.449, 433 runs
Generally speaking, any team from the 2000s that was at least halfway decent offensively usually managed around .270 or better at home and was usually at least a little worse on the road. Also, since MMP opened only four Astros teams have hit worse at home than on the road: 2018, 2017, 2016, and 2006 (.254 vs. .256, and they still had higher OBP and SLG at home and scored more runs at home).
I've seen some speculation online that the hitters may not be able to see the ball as well at MMP for some reason. I think this is extrapolating from quotes from a couple of players over the last road trip who said they liked playing in Oakland because they could see the ball well. It does sound at least a little plausible. In 2016 the stadium lighting was replaced with LED, and I think I remember Springer saying early in that season that he had to adjust to the glare from the new lights while playing the outfield. In 2017 they got the new batter's eye which is a brighter green color than what used to be behind Tal's Hill.
Now, that wouldn't explain how last year's team had offensive success at MMP not seen since the powerhouse 2000 offense, nor would it completely explain the huge dropoff this year. But it's interesting to consider.