LONDON—Oil prices plunged on Thursday, while OPEC+ stuck to its existing deal for May output. Brent crude futures for May, which expire on Thursday, were down $5.91, or 5.21 percent, to $107.54 a barrel by 1253 GMT. The most actively traded June futures were down $5.53 at $105.91, after falling by $7. U.S. West Texas Intermediate futures for May delivery was down $6.06, or 5.62 percent, to $101.76 a barrel, off a low of $100.16. The Organization of the Petroleum Exporting Countries and allies including Russia, known as OPEC+, agreed at a meeting on Thursday to stick to its existing agreement and raise its May production target by 432,000 barrels per day (bpd). “In the light of the overnight developments, the OPEC+ decision seems to be a non-event. The increase of 432,000 bpd has been expected and built into the price. The decision will be greeted with disappointment from consuming …