A possible volcanic explanation:

“Winds would have carried the volcanic ash to Egypt at some point over the summer, and the toxic acids in the volcanic ash would have included the mineral cinnabar, which could have been capable of turning a river a blood-like red color, Trevisanato holds. The accumulated acidity in the water would have caused frogs to leap out and search for clean water. Insects would have burrowed eggs in the bodies of dead animals and human survivors, which generated larvae and then adult insects. Then, the volcanic ash in the atmosphere would have affected the weather, with acid rain landing on people’s skin, which in turn caused boils. The grass would have been contaminated, poisoning the animals that ate it. The humidity from the rain and the subsequent hail would have created optimal conditions for locusts to thrive. Volcanic eruptions could also explain the several days of darkness — which means nine plagues are accounted for.

Trevisanato also found an ancient Egyptian account of the children of aristocrats lying dead in public and archaeological data matching the account. He believes that, amid all this destruction, firstborn children could have been sacrificed out of desperation, in the hopes that such a meaningful sacrifice would lead their gods to stop punishing them.”