Fast dying veggies-- Help!

If your weather has been like mine in SE Minnesota, it has been a really hot summer, not as hot as you get, but started out early this year with hot weather. The plants all enjoyed the early warmth, but have required a lot more water this year. I have a bush Early Girl tomato in a huge pot and it is now at least 6 feet high(just the plant) and has a 2 1/2 to 3 gallon water habit a day. I have to give it three watering's a day or it starts to wilt. Perhaps you need to water your outside plants more than once a day. If they are in pots they need more watering because they don't keep the moisture as well as in the ground. I definitely water my pots more than I do my in ground gardens. I have a meter that gives you the moisture level by inserting the rod into the soil, easy to use, all you have to know is the moisture requirements of the potted plants you have, I'm sure it would work on the in ground gardens too. I have a black thumb for indoor plants, so my hubby takes care of them. I have made a few booboos outdoors in all my years, but seem to have luck with any outdoor plants in pots or in ground. Go figure! The meter is sold in a lot of places. We just replaced my 30 year old one with one from Menards for about five dollars. I have seen them at Walmart, home depot also. Avoid them at garden places as they are usually over priced. Thirty years ago they were hard to find and very expensive, I think mine was like thirty five dollars back then, but then again it comes out to about a dollar a year! Good luck with your plants!