LTE is going to have different propagation / building penetration characteristics than the bands that it is replacing. If you are really in a fringe area, this could be bad. Throw in that the phones might not switch over to 3G and that can be an Rx for disappointment, right?
But I think in this case, the poster is commenting that their 4G/LTE bandwidth was previously good, and has degraded...
Could be a tower issue, or could be a capacity issue.
Try running a Speedtest at different times of the day to see if it's a capacity issue. If so, likely your speed for download and upload are going to get better in off peak usage hours.
Then again, use one of those Signal Info apps to determine which of potentially a few towers are serving your phone's connection. See if changing your location results in higher speeds... Maybe a tower getting maxed in that ZIP.
I recommend LTE Discovery or Network Signal apps. Speedtests can KILL your data at 30-90 MBs per test depending on the area, signal, and speed. I tried this when going through the initial discovery of poor signal and speed around me at Verizon's behest for testing purposes. I used 30MBs at home on a test and a couple blocks over I hit 75MB used for a single test. On a 1GB plan, that killed 20% of my month's use.
LTE Discovery I found was good to show both the Voice signal and the Data signal individually, since some people's status bars show LTE bars and someone might not ever know their Voice strength without having to go through all the network menus on the phone.