It could be that availability in the lower fare class that sold for $141 does not have 4 seats available, so that's why you're getting a higher price. Try searching for 1, 2, 3 and then, 4 seats and see what results you get. You may be surprised by what you notice.
Also, keep in mind that prices usually go up on weekends as that's when most people usually have time to make travel plans. If you wait a few more days until Tuesday afternoon (after 3pm ET), you may be able to find the cheapest options there.
For domestic travel, a lot of sites don't advise buying so much in advance - about 3 months out will be much better - so, for travel in July, probably start looking in April. With a party of 4, may not want to chance it but here's a website you can look at with tips and everything I mentioned:
http://traveltips.usatoday.com/airli...est-56973.html
Good Luck!