Browning leaves, at this time of season, in zone 4 should be normal. Even temps in mid 50s is more like fall weather.

Another factor is inherited in container gardening. Normally you would want to cut back on fertilizing at this point. This should be fine for in ground plants but in case of potted plants it can mean nitrogen deficiency. But IMO, that is ok. You want the fruits ripen and not any foliage anymore.

T...mine are actually winding down a bit in zone 10! The above comments seem fair...also your point of becoming rootbound by now are accurate. There are definite advantages to container growing...but a few pitfalls, as well.